Critical Hits: System I (POCT)

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==Critical Hits: System I==
Critical hits occur when a character rolls a natural 18 or higher and hits the target by a margin of 5 or more after all adjustments. If the character scores a critical hit, he inflicts double damage dice, calculated before adjustments for Strength, magic, or special circumstances. In a situation where the damage is doubled for another reason, do not double the multiplied damage; add it instead, then add other adjustments. For example, a light lance inflicts 1d6 damage, or 2d6 in a charge. But if a charging lancer scores a critical hit, the lance inflicts 3d6 damage, not 4d6.
For example, Liera is a 4th-level elven warrior fighting a gnoll. Liera's base THAC0 is a 17, but she has a 17 Strength (+1 to hit), she's an elf using a long sword (+1 to hit), and she has a magical long sword +2. Her total adjusted THAC0 is 13, and the gnoll's Armor Class is 5. She will hit the gnoll on a roll of 8 or better, and can achieve a critical hit with a natural 18 or higher. On one combat round, she rolls a 19, which is a critical hit. She rolls 1d8 for damage, doubles that, then adds +1 for her Strength and +2 for her magical long sword, for a total of 15 ((6x2=12)+1+2).
After dispatching the gnoll, Liera finds herself facing a horrible tanar'ri with an AC of –3! She scores a hit on a roll of 16 or better. She cannot score a critical hit because it's impossible for her to hit with 5 points to spare; even if she rolls a 20, she only hits by 4. If the tanar'ri charged, its AC would drop by one point to –2, and then Liera could score a critical hit with that roll of 20.
There are no specific injuries using this critical hit system. Instead, it only provides characters and monsters the chance to dish out extra damage when they make a great attack roll. Limiting the critical hits to attacks that hit by a margin of 5 or more solves one other problem. Consider the 1st-level fighter. He only hits on a 20 against an opponent with very good Armor Class (0 or lower). Under other critical hit systems, the few times he does hit, the fighter automatically inflicts a critical hit. Under this system, that can't happen.