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What is THAC0?

THAC0 is an acronym for:

To Hit AC (Armor Class) 0 (Zero).

Remember the following is a Quick & Fast idea of THAC0. Be sure
to read the Players HandBook.
I also reccommend talking to an experianced player / DM personally.


For Example say you have a character who has a THAC0 of
say 15. By the above statement you would need to roll (on a d20) 15 or
higher to hit a creature, person, or object (to be hereafter refered to
as an opponent) with an AC (armor class) of Zero.
Of course you are probably wondering what to do when you attack an opponent
who has an AC of say 5 or -5.
Well it's simple. If you attack an opponent with an AC of 5
you would subtract 5 from your THAC0. So if you had a 15 THAC0
you would now need to roll a 10 or higher (on a d20) to hit
your opponent. The reverse is true with an opponent with an
AC of -5. You would add 5 to your THAC0. Therefore you would
need a 20 or higher on a d20.

THAC0 Adjustments & Rolling Double Damage

THAC0 Adjustments are given by ABILITY scores (i.e. high strength,
dex, etc) might contribute to a THAC0 adjustment. Also Magic Weapons
and items may improve or hinder THAC0.
Say you have a THAC0 of 15 and acquire a Long Sword +2. This magic weapon
gives you a +2 to hit and a +2 to damamage. Therefore effectively lowering
your THAC0 to 13. This is how you can roll above a 20 on a d20. For example
say your roll a 19, and have +2 sword, that means you really rolled a 21.
That is called an UNNATURAL number. If you had rolled an 18 and factored in a
+2 you rolled an UNNATURAL 20 which does not cause double damage or automatically
hit. However remember it is possible to go the other way. You could get a cursed
Long Sword +2, that would raise your THAC0 to 17.


Rolling a natural 20 (in other words the die reads 20) on a d20 will result in
an automatic hit doing double the damage you roll, any strength bonuses are
added last and not doubled. However this automatic hit will not do you any good
if you are attacking a creature that requires a magic or silver weapon to hit.
For example say you roll a 20 (on a d20) while attacking a werewolf, which
requires a magic augmented or silver weapon to hit, and you are attacking the
werewolf with a normal long sword. Well you automatically hit and did no damage.
At the DM's discretion you could have knocked the creature off balance, but you
did not physically injure it.


Rolling 1 on a d20 will result in a critical error. This means not only did you not
strike your opponent, but you did something like trip, drop your weapon, smash a finger,
fall on your own sword, etc... I think you get the picture, it's up to the DM as to how
bad you got screwed. But remember DM's if you kill a character off, unless the situation
meritied it you'll really just be pissing of the player(s). The point of the game is to
have fun notto rack up character kills.

If for some reason you think I have stated a rule incorrectly please tell me
about it and be sure to reference your statment. (i.e. player Hand Book page# etc.).

For more information about rules or etc, please contact -Sam-.