Converting THAC0 to Hit Bonus

THAC0. “To Hit Armor Class 0”. How does one convert this to a modern equivalent of a hit bonus when looking to use older modules & monsters in a modern game (such as DCC RPG, or D&D 5e)? As a follow up to my investigation into ascending vs descending armor class, I now offer my interpretation on how to simply convert THAC0. Or not… as it turns out, this wasn’t as nearly as easy as I’d hoped..

TL;DR: There is no easy conversion, but as a start, use table 2 below, and assign the THAC0 to the D&D 5e proficiency bonus as a hit bonus and then add your other modifiers (i.e. strength bonus) for either 5e or DCC.

First off, if you want a basic explanation on how to use THAC0, a good blog post is here and some explanation on the origin here. Basically, I refer to one of the comments in the first link to sum up how one uses THAC0 in an original game:

THAC0 – (d20 roll + mods) = You hit anything of this AC (or higher)

But, that doesn’t really help me too much for what I want to do…

So, maybe the D&D 5e conversion guide has something? And I’ll just use that for DCC RPG? Unfortunately it doesn’t mention anything about THAC0. I’m out of luck there.

Swords & Wizardry uses both an ascending and descending AC, and uses THAC0. But I’m finding there are some discrepancies in the math, which I’ll skip over for now. But it may be a start if you want to look at it, and look at Tenkar’s rules of thumb for converting to pluses.

Maybe if I look at the “base” THAC0 and start there? It is 20. Meaning that at level 1, with no modifiers, to hit an unarmored target (AC 10), you need to roll a 10 or higher. So, essentially, this is like having “no” hit bonus. Now,  what happens when a player levels up? This THAC0 sequentially goes down (or is it “Increase” since you’re getting “better”?… so confusing…), and this is linear for the fighter. Based on this, I made a table with a simple inverse, linear, relationship. Turns out this doesn’t really work out; but it’s easier to show than tell:

Table 1. A Simple Inverse Linear Relationship

THAC0 Hit Bonus
20 0
19 +1
18 +2
17 +3
16 +4
15 +5
14 +6
13 +7
12 +8
11 +9
10 +10
9 +11
8 +12
7 +13
6 +14
5 +15
4 +16
3 +17
2 +18
1 +19
0 +20

If you now compare the fighter in AD&D, 2e, and 5e, and the Warrior in DCC RPG, you see that this Table 1 doesn’t really match up. 5e is “flatter”.

Table 2. Comparing Across Editions

Level* AD&D 1e** AD&D 2e D&D 5e DCC*
THAC0 THAC0 Proficiency Bonus Deed Die
1 20 20 +2 +d3
2 20 19 +2
3 18 18 +2 +d4
4 18 17 +2
5 16 16 +3 +d5
6 16 15 +3
7 14 14 +3 +d6
8 14 13 +3
9 12 12 +4 +d7
10 12 11 +4
11 10 10 +4 +d8
12 10 9 +4
13 8 8 +5 +d10+1
14 8 7 +5
15 6 6 +5 +d10+2
16 6 5 +5
17 4 4 +6 +d10+3
18 4 3 +6
19 4 2 +6 +d10+4
20 4 1 +6
* I am using a convention that one level in DCC is equal to 2 levels in any edition of D&D.
** I think... I found this on a thread; I can't make heads or tails of any of this by reading the AD&D PHB or DMG; and the table in OSRIC is a little different.

Looking at table 2, I come to a few observations based on a level 9 D&D fighter (or level 4 warrior) as a test:

  • Whereas table 1 would convert to a +8 hit bonus, the level 9 D&D 5e fighter has 1/2 this proficiency bonus of +4; so table 1 isn’t close to the same; i.e. this is not a simple inverse relationship (I can’t find any links, but I believe Mearls referred to a “flat math” when designing 5e).
  • However, I find it interesting that the level 9 DCC Warrior in ‘some’ ways is similar. That is, if you looked at the maximum possible deed die result of +7 compared to the predicted +8 on table 1. But, of course, with the random nature of DCC RPG, you’re equally as likely to roll a +1. So, that doesn’t really match 1e and 2e either. HOWEVER, it is equivalent to D&D 5e as the average result of a d7 would be +4.
  • Keep in mind that in D&D 5e, proficiency bonuses are the same per level, regardless of class.

To make this even more confusing, the THAC0 tables for all the other PC classes are different, and monsters use a table based on Hit Dice.. and the table in the 2e DMG is confusing on this… God forbid I can figure any of this out in the 1e AD&D PHB or DMG…. and then 1e is different than 2e….. and this THAC0 stat isn’t used for anything else in the game but combat…… I’m sorry but all those comments that respond “oh, but THAC0 is easy, you just subtract this one number from another number….”, you’re missing the fucking point; as a whole, this is confusing as shit!

One more Table

As just mentioned, Monsters use Hit Dice instead of level (and class) to determine THAC0. You might need this table since my whole point of this is to convert weird monsters found in old modules and references.

Table 3. Creature THAC0 in AD&D 2e

Hit Dice THAC0
less than 1 20
1 19
2 19
3 17
4 17
5 15
6 15
7 13
8 13
9 11
10 11
11 9
12 9
13 7
14 7
15 5
16 or higher 5


Based on these observations, I conclude that there is no simple conversion. How’s that for a conclusion! Ha!

However, you can probably use table 2, and just take the THAC0 listed, and then cross reference to the appropriate D&D 5e level and assign that proficiency bonus as the “to hit” bonus. Obviously, you then add any other hit modifiers as usual (i.e. strength bonuses) and I think that will be helpful to start.

This is merely meant to be a simple conversion to create a starting point. I assume that common sense should guide any further modifications. And, when in doubt, I recommend that you should round up (in favor of the monster!).

Using Tarot in the Creation of Adventure Ideas

Snow Queen Tarot Reading
Snow Queen Tarot Reading

Finally. A few days off from work! Woot!

I stopped by a trippy spirituality shop today and I was thinking (dangerous, I know…) that surely there’s something I can use here for inspiration. I gravitated to the basic run of the mill Rider Waite tarot card decks. I used to have a set of these back when I was in college. I’d whip them out at bars and tell fortunes to girls. Yes. I’m that big of a geek. And, if you’re wondering, yes, it worked 😉 [well, a lot more than you’d probably guess!]

I also received my print copies of D.A.M.N.! #1 and #2 in the mail when I got home and I was flipping through there and further became inspired by the level 4 adventure, “The Snow Queen” by Garett Oliver. I’ll be honest, I barely read past the introduction as there is a break out box “Expanding the Adventure” and that’s where I said “I like the idea of a Snow Queen, and my dudes are in a snowy Hyperborean area, and hey I’ve got some tarot cards to do something with!”

The following is extremely busy. I am basically copying and pasting my notes. I simply started my Black Sabbath playlist, asked the question “What is the origin of the Snow Queen” and started laying down cards.

I like an 11 card version. Starting with a significator card (here, it represents the Snow Queen) followed by a Celtic Cross on top. See the pic above for the exact spread.

Red text is my interpretation as I go through this.

Significator: Ace of Swords, reversed
Ace of Swords
Ace of Swords

Background: The person or thing about whom or which the inquiry is made. Swords correspond to persons with dark brown hair and possibly gray, hazel or even blue eyes.

The Snow Queen is a tall thin elven built woman of pale complexion “white as snow” with beautiful long dark brown hair and pale blue eyes. Also, the Ace card is #1 in the suit; which I’m telling you right now, tarot can be eerie weird like that… right away, a #1 card to represent the #1 in this queendom.

Description of Card: A hand issues from a cloud, grasping a sword, the point of which is encircled by a crown.

The Snow Queen wears a finely wrought gold crown and carries a menacing yet beautiful sword at her hip. She was given these items by a god who descended from the sky and anointed her the ruler of her people.

Divinatory Meanings: Triumph, the excessive degree in everything, conquest, triumph of force. A card of great force, in love as well as in hatred. Since this is reversed, the results are disastrous; another account says — conception, childbirth, augmentation, multiplicity. Reverse of Reason and Logic. Fear.

At her peak, The Snow Queen was an extremely powerful sorcerer queen. The only thing she loved more than absolute power was a lover (name? background?). She went mad when she conceived an abomination with this lover. 

The Snow Queen has gone mad. She is delirious. Hallucinates. Furthermore, she is paranoid.

She may have the ability to cast a spell “Fear”.

“That covers her” : X of Cups

Background: This is the person or thing’s general environment at the time. Cups are assumed to represent people with light brown hair and of fair complexion

This person is not of the same race as The Snow Queen.

Description of Card: Appearance of Cups in a rainbow [eerie note: it is “pride” month right now…lol I told you Tarot can be weird!], it is contemplated in wonder and ecstasy by a man and woman below, evidently husband and wife. His right arm is about her, his left raised upward as she raises her right arm. The two children dancing near them have not observed the prodigy, but are happy after their own manner. There is a home scene beyond.

Wow, OK, so the downfall of The Snow Queen may have something to do with this extra racial lover of hers, and the family they tried to create, yet there was a fall. Or maybe her lover was the same gender? Awesome, lesbian elves…. !! Maybe they undergo some sort of ceremony or ritual trying to have a child/children and that is the basis of “the abdomination” I thought up above? Either way, maybe this went well at first, but then later fell apart.

Divinatory meanings: Contentment, repose of the entire heart — the perfection of that state, if with several picture cards, a person who is taking charge of the Querent’s interests. Also the town, village or country inhabited by the querent. Tranquility

Yes, maybe there was a “contentment of the entire heart” initially. “All was perfect”. This was initially good for her Queendom and as she fell, so did they.

“This represents her obstacles” : The Sun, reversed

Background: If it is a favorable card, it will be something good in itself, but not productive of good in the particular connection.

Divinatory meanings: The reverse of, or “in a lesser sense”: Material happiness, fortunate marriage, contentment, unhappiness. Troubled relationships. Broken engagements and contracts. Misjudgment, delays, potential failure, inflated ego.

The Snow Queen had all the material happiness one could hope for, being that she was the Queen of the Northern Elven empire. Her downfall began with a troubled relationship. She misjudged the impact of falling in love with a non-elf (human? Oh. maybe a demon or half demon). She was a victim of hubris. Maybe she had made some deal with someone/something and reneged? Maybe this is the source of breaking a contract with the demon/devil she had sought to bring her relationship together.

“This crowns her” : The Moon, reversed

Background: It represents (a) the best that she can arrive at, or (b) her ideal in the matter; (c) what she wants to make her own; (d) but it is not her own at the present.

Divinatory meanings: Instability, inconsistency, silence, lesser degrees of deception and error.
Fear, confusion, highly charged emotions, bewilderment, lies, deceit. Despair and a desperate need for help. Insincerity.

As she falls from grace, she begins to become all these things. Wide mood swings. Deep despair. “Why is all this happening to me?”. Delirious. Paranoid. Lying and unfaithful to someone/something. Or infidelity creeps into the relationship.

“This is beneath her” : IV of Cups, reversed

Background: It is her own — that which she has to work with and can use.

Description of Card: A young man is seated under a tree and contemplates three cups set on the grass before him. He expresses discontent with his environment. An arm issuing from a cloud offers him another cup.

Divinatory meanings: In it’s upright form, this represents weariness, disgust, aversion, imaginary vexations — as if the wine of this world has caused satiety only. Another cup of wine, as if a fairy gift, is now offered him, but he sees no consolation therein. However, this is reversed —Novelty, omen, new instructions, new revelations Despair

This cup is offered from a cloud. In the significator card, The Snow Queen is given her crown and sword (her authority and power) from a cloud. In this card I see that a being fools her as a ruse making her believe it is her god, offers her new instructions, new revelations. But it is a lie that only leads to despair. Nevertheless, this is the source of her new power and makes her who she is now.

“This is behind her” : VI of Cups, reversed

Background: It is the current from which she is passing away, and it may be the past of the matter.

Description of Card: Children in an old garden, their cups filled with flowers.

Divinatory meanings: A card of memories and of the past. For example, reflecting on childhood, happiness, enjoyment, but comic rather from the past, things that have vanished. Another reading reverses this, suggesting new revelations, new environment and new knowledge. Reversed: Renewal, the future, that which will come to pass presently Ignorance

The Snow Queen had to give up all that was good in the past in order to move forward. She sacrificed all those close to her. Her children. Her lover. Her subjects. In a blood pact “her cup runeth over with the blood of the innocents” Ignorant that she was being duped in her pact with a new demonic patron.

“This is before her” : V of Pentacles, reversed

Background: It is the current that is coming into action and will operate in the specific manner.

Description of Card: Two mendicants in a snowstorm pass a lighted casement.

Divinatory meanings: It foretells material trouble above all, whether in the form illustrated, that is, destitution, or otherwise. For some cartomancists, it is a card of love and lovers — wife, husband, friend, mistress — also concordance, affinities. These alternatives cannot be harmonized. Reversed: Disorder, chaos, ruin, discord, profligacy. Fresh Ideas

Her new pact involves “marrying” this devilish patron and embracing chaos, which is followed by ruin of her queendom and separation from the greater Elven empire.

“Immediate Future” : The Star, reversed

Background: Signifies her self, her attitude, and relation to the matter.

Divinatory meanings: Loss, theft, privation, abandonment, although another reading suggests hope and bright prospects in the future. Reversed: arrogance, impotence, haughtiness. Self-doubt, lack of trust, cynicism, pessimism, inability to freely express oneself. Rigidity of mind. Obstacles to happiness.

This sums up the current mental state of the once Snow Queen. She has become arrogant, haughty, distrustful, cynical and inflexible.

“Surroundings at Present” : VI of Pentacles, reversed

Background: Signifies her house, her environment in the affair — the influence, people and gents about her.

Description of Card: One in the guise of a merchant weighs money in a pair of scales and distributes it to the needy and distressed.

Divinatory meanings: Presents, gifts, gratification. Another account says attention, vigilance, now is the accepted time, present prosperity, etc. Reversed: desire, cupidity, envy, jealousy, illusion. Greed

The remains of the Snow Queens realm has become a center for nefarious crime syndicates or reavers who raids other villages, rapes and pillages. Her spies infiltrate bordering lands. Subterfuge. Extortion. Maybe plays other organizations against each other for the profit of the Snow Queen.

“Hopes & Fears” : Queen of Wands

Background: Signifies her hopes and fears

Description of Card: Throughout this suit the wands are always in leaf, as it is a suit of life and animation. Emotionally and otherwise, the Queen’s personality corresponds to that of the King, but is more magnetic.

Divinatory meanings: A dark woman or a countrywoman, friendly, chaste, loving, honorable. If the card beside her signifies a man (the one above and below are men) she is well disposed towards him (but both of these are reversed, so I’ll read as ill-disposed). Love of money. Compassion

At some unconscious level, the Snow Queen hopes she can return to her prior grace. Or she fears that a new, noble and honorable woman will defeat her. This may point to a prophecy leading to her downfall. The Queen is #13 in a suit. This is an unlucky draw for the card which represents hopes and fears.

“The Outcome” : VII of Pentacles, reversed

Background: Represents what will come. It is on this card that you concentrate your intuitive powers, your experience and your memory in respect to the official divinatory meanings attached thereto. It should include whatsoever you may have divined from the other cards on the table, including the Significator itself and concerning her, not excepting such lights upon higher significance as night fall like sparks from heaven if the card which serves for the oracle, the card for reading, should happen to be a Trump Major.

Description of Card: A young man, leaning on his staff, looks intently at seven pentacles attached to a clump of greenery on his right. One would say that these were his treasures and that his heart was there.

Divinatory meanings: These are exceedingly contradictory, in the main, it is a card of money, business, barter — but one reading gives altercation, quarrel, and another innocence, ingenuity, purgation. Reversed: anxiety about money. Decline

Maybe it is the growing wealth which The Snow Queen is rumored to have accumulated, that draws the attention of heroes.

Solitude from Black Sabbath is the song currently playing… let’s google the lyrics…

My name it means nothing, my fortune is less

My future is shrouded in dark wilderness

Sunshine is far away, clouds linger on

Everything I possessed - Now they are gone

Oh where can I go to and what can I do?

Nothing can please me only thoughts are of you

You just laughed when I begged you to stay

I've not stopped crying since you went away

The world is a lonely place - you're on your own

Guess I will go home - sit down and moan.

Crying and thinking is all that I do

Memories I have remind me of you

Work this in some way; I think it is perfect. Holy crap, I told you Tarot is weird! As I read this, this is exactly her mind as she goes crazy and has bouts of remembering “everything I possessed, now they are gone” and “nothing can please me only thoughts are of you”. She goes into great despair. She is lonely and actually seeks release from her misery. She will defeat herself as she is otherwise immortal and is forsaken to live this evil and miserable existence. Maybe a prophecy tells of the man in the VII of pentacles redeeming her and releasing her from her fel pact. Or maybe just putting her out of her misery. Either way, there is a disappointment in the end (being that the card is reversed). At the very least, the rumors of wealth. But maybe that fails too in the end. Maybe she has been feeding all of her wealth to her demon. Like it feeds off it or something, like how these pentacles are growing on a vine like ripe fruit. Fruit for the demon using the Snow Queen to mamas its needed sustenance.

A couple other observations:

There are multiple cups and pentacles. Use these themes somehow.

For example, the suit of cups is associated with water and emotions. This plays to the emotional connections going throughout this reading with relationships, betrayals, and brash decisions. Water is a feminine element and associated with ice and snow.

Pentacles is associated with physical and external forces of consciousness. In popular culture, pentacles are also associated with black magic. All of these tie in with a  demonic force at play.

There are a lot of reversed cards. I had initially thought of this being underground somehow; this reinforces that idea. After “the pact” the city “fell” or “sunk”. It also reinforces any ideas of a “fall from grace” and that everything has “turned upside down” for the Snow Queen. Make this a tragic story. In her unconsciousness she knows what she did. The Snow Queen was once beautiful, beloved, and powerful. But now…

How far does a Dungeon Master go?


How far do you go, as a Dungeon Master, Game Master, or Judge, to steer PCs toward special treasure or effects? Stuff that you probably just as much want to see your friends find (and play with) as you’re hoping they will.

For example, in Sailors of the Starless Sea 2nd printing (for DCC RPG), the PCs investigate the hot pits in H-1, but keep wimping out, not to go down further. This is understandable as it is clearly dangerous, but now they miss any opportunity to acquire the Fiend-Blade or a Blessing of the Slow God. Despite me even encouraging them to return later (I mean, it’s a perfect place to thaw out a decades old frozen Chaos Lord…)

Then, a PC actually pulls the bronze ring in the pool in 1-2, survives, and falls into 1-3, but then never even says anything about “oh, let me look around here”. So, it’s not like the Band of Fire is just going to slip onto his finger (ala The One Ring, although now I think of it, I probably missed an opportunity to play it like that!) I give a little extra description to entice further exploration, but it’s like survival kicks in and the priority is simply to get out ASAP, and so the legendary ring remains in the much covered in hundreds of old skulls.

So, a DM, should be “Neutral”, yet I think we also ought to be cheerleaders for the PC’s.

But like a cheerleader, we cannot actively affect the outcome of the game. Yet, it drives me nuts in my OCD brain thinking of cool things that totally go unnoticed simply because a PC won’t at least say “I want to look X to see if there’s anything there amongst all of the A’s, B’s and C’s you just described as being there”. And, I’ve learned that there’s no fun at all just giving them an uncalled for “passive perception” type of roll to do it for them.

If the item, place, etc. is truly necessary for the game, then I see three options:

  1. Make multiple way for the PCs to come across it
  2. Should be rare, but sometimes you have to hit them over the head with it if the DM and PCs simply aren’t on the same wavelength (i.e. if you feel it’s “your fault” and not describing the situation accurately.)
  3. An option for stellar DMs, improvise around it. The PCs don’t find the widget that saves the kingdom at the last minute? Fine. The Kingdom falls. Tear up the last couple sheets of paper you have in your binder and the DM rolls right into describing the chaos that immediately ensues. Roll for initiative motherfuckers! Muahaha!

However, if the loot or what have you, is not necessary for the outcome of the story, then I believe the answer is to simply keep a poker face and don’t ever let on to the PC’s that they just passed up a Vorpal Sword or similar. If your doodad is extra special and you really want to see it in game, then your option is to just put it somewhere else. Maybe in your next game you create a special little add-on area (that they overlook again… uggh…). Or maybe a villain finds it! The über boss at the end of this adventure (or the next?) is now tougher, richer, and has his own castle because he came across the Deck of Many Things that the PCs passed up!

Any other thoughts?

Happy Black Friday Delivery Day!

Best Dungeon Mastering Advice

Best Dungeon Mastering advice I’ve received to date. Goes something like this:

“RPGs are like sex. So long as everyone involved is having fun, and keep coming back for more. You’re doing it right.”