How do I make an attack with a flat damage modifier instead of using damage percents?

While there is not a built-in feature for flat damage modifiers, you can use attack chains to achieve the same effect.

1. Use an attack that does not do any damage to store a target. If the attack misses, you can use the "do not chain if attack fails" bitset to avoid problems with the rest of the chain.
2. Use an attack on the caster to increase the attack or magic temporarily, using the "100" attacking stat and "Pure Damage" as the attack type, targeting the stat you want to increase or decrease. Use both "Cure instead of Harm" and "Allow Cure to Exceed Maximum" in order for this to work.
3. Use the actual attack, using the recorded target as the target.
4. Use an attack on the caster that undoes the stat gain done by re-damaging the caster's attack/magic. Restore Target Stat to Maximum is not recommended due to other spells that could affect the stat in use.