Nothing I’ve seen has provoked so much controversy within the old school community as ascending versus descending armor class. Labyrinth Lord, like B/X, uses a combat matrix with to hit rolls against descending armor class. Basic Fantasy RPG and DCC RPG, like 3.5, use an attack bonus versus 10+ ascending armor class. Swords & Wizardry splits the difference.
What does ACKS use? Well, neither. With ACKS, we started by acknowledging that all the player really cares about is “what number do I need to roll to hit”. We wanted to find the absolutely easiest way possible to deliver that information. It turns out the system we needed was there all along, in the form of B/X saving throws. Everybody immediately grasps how old school saving throws work. If you have a Saving Throw versus Poison of 14, that means you’ll need to roll a 14+ or succumb to the poison! It’s clear just from looking at the character sheet what the player has to roll on the d20 to succeed.
Following this logic, in ACKS, each character gets an “attack throw” value - this is the number he needs to roll to be successful at attacking ( just like a “saving throw” value is the number needed to roll to be successful at saving.) A normal man’s attack throw is 11+, meaning he needs to roll an 11+ on 1d20 to hit.
Armor makes a target harder to hit. The target’s Armor Class is added to the attack throw value necessary to hit it. A target with zero armor has, intuitively, an armor class of zero. A target with leather armor has an AC 2, while one with platemail and shield has an AC of 7. If your attack throw is 11+, and your target’s AC is 2, you will hit the target on a roll of 13+.
Converting to the ACKS “attack throw” system is easy, and once you use it, we think you’ll find it the most intuitive to hit/armor class system yet. To convert –
- From B/X: ACKS AC = 9-AC; ACKS Attack Throw = THAC0-9
- From 3.5: ACKS AC = AC-10; ACKS Attack Throw = 11 - Base Attack Bonus