Sorry for the late post, its saturday now. I wanted to make a simple mod to d20 to have less hp bloat and have only one hitdice. I realized halfway through that you can just convert WOD or Ars Magica to dnd instead.
Its like this.
1. Roll 1d6 for initiative for each character. Higher numbers go first.
2. When its your turn, you get a movement and an attack in any order.
3. When attacking, roll a D20 and then compare it to the target’s defence. If it beats the targets defence, the attack hits and roll for damage. If it doesn’t beat the target defence, the attack misses.
4. After everybody has acted, start at the beginning of the initiative order.
After rolling a successful hit, roll the weapons damage or 1d6 if not specified. Then add any modifiers then subtract the targets Armour value from the damage total.
If damage done is more then the targets current hit points, the target takes 1 fatigue.
As battles continue, PCs and NPCs begin to tire and fatigue begins to take in. Depending on the type of armour worn, you will be gaining fatigue every 5 combat rounds or 10 combat rounds.
When you gain fatigue two things happen.
-Your evasion decreases -2
-Your armour reduction decreases by -1
Fatigue can stack, but it can not reduce evasion or armour reduction to negative numbers.
The amount of fatigue points a PC or NPC can take is dependent on their max hit points.