... now with 35% more arrogance!

Monday, June 29, 2020

Severity of Attack

There’s a certain elegance in letting the attack roll also equal the severity of the blow. In other words, the higher the roll, the more likely that a successful attack is a critical hit. OD&D has this buried in the monster descriptions under Purple Worm:

Any hit which scores over 20% of the minimum total
required to hit, or 100% in any case, indicates the
Purple Worm has swallowed its victim.

In other words, four points above the target number, or a natural 20, is a critical hit with a special effect (swallowed.) The Greyhawk supplement uses the same mechanic for the Sword of Sharpness, with a critical hit with the special effect “Sever Limb or Head”.

This is a kind of clunky mechanic, especially for either the THAC0 or d20 System approach, but a d20 roll-under system would simplify it:

  1. Add Descending AC and either fighter level or monster hit dice together to get a target number.
  2. Roll 1d20. If result <= target number, attack is a success.
  3. Result rolled, if successful, is the severity.
  4. Severity 4+ is a critical hit with a special effect.

Delta’s Target 20 System can also work, but the last digit of a successful result (20+) is the severity, with the understanding that any result of 30 or more is Severity 9. Again, Severity 4+ is a critical hit with a special effect.

But what are those special effects? That’s something I plan to expand on in a follow-up post.

Creative Commons license

This work is licensed under a Creative Commons
Attribution-NonCommercial-ShareAlike 4.0

(CC BY-NC-SA 4.0) license.


  1. I blogged about something similar a few years ago if you’re interested https://deathanddismemberment.blogspot.com/2015/03/the-challenges-20-expanded-combat-table.html

    I ended up making a more refined version which made its way into my house rules doc but warning its about 20 pages long

    1. Thanks for the link!

      You might want to compare that to the follow-up post I have planned for tomorrow. I do have a table (two tables!) and something similar to your combat tricks (but limited to physical effects. I don't use a lot of "+1 damage"/"+3 damage"-style results, though.