Damage

Every spell hit and every damage effect hit goes through the same 15 steps, in this order. Steps that only apply to one kind of hit say so.

1. Every hit waiting in the queue. Every hit waiting in the queue is handled once per frame. A hit on a shielded enemy is dropped by the shield and skips every step below. Every other hit runs the steps in this order.
2. The starting damage. The starting damage is picked (see the two lines below), then it is multiplied by the hit's own multiplier, which is never allowed below 1, and the hit's own flat addition is added.
3. Starting damage of a spell hit. A spell hit that carries no starting damage of its own uses the spell's damage. Jam, and every spell cast while Chicha's Aeon state is upright, instead roll a random number between the spell's minimum damage plus the Min Damage bonus and its damage plus the Max Damage bonus.
4. Starting damage of a damage effect hit. A damage effect set to deal damage equal to the target's health starts from that enemy's maximum health instead of its own damage.
5. The modifier steps. The modifier steps below run in order, spell hits through the spell path and damage effects through the effect path.
6. The spell's own damage stat. The spell's own damage stat is applied to the starting damage, then the sigil bonus and the patient caster bonus are added on top.
7. The damage effect's own damage stat. The damage effect's own damage stat is applied to the starting damage.
8. Percentage adders carried by the hit. Percentage adders carried by this one hit add starting damage multiplied by their total.
9. Familiar damage. A hit marked as familiar damage adds its starting damage multiplied by Familiar Strength.
10. The target's own numbers. The run's damage bonus for that kind of target is added (the bonus against normal enemies, or the bonus against elites), then the enemy's own damage amplification is added, then the result is divided by the enemy's damage reduction.
11. The final multiplier and divider. The hit's final multiplier multiplies the result and its final divider divides it. Neither is allowed below 1.
12. The crit. Unless the hit is marked as never critting, the crit roll happens here and the crit bonus is added as a separate number.
13. The flat bonus. The hit's flat bonus is added last, after every multiplier.
14. The enemy takes the hit. The enemy takes damage plus crit. The hit counts as a kill when the enemy's current health is at or below that total.
15. A shielded enemy. A shielded enemy takes nothing at all. The shield eats the hit.

One Fireball hit on a normal enemy, with a run that has picked up 50% Spell Power and 20% damage against normal enemies, and with the enemy at no damage reduction and no damage amplification. Every other number below comes straight from the game data: Fireball deals 10, Spell Power and the damage bonus against normal enemies both start a run at 0 and 0, and Crit Damage starts at 1.

The crit is added as its own number rather than multiplying the hit, which is why a crit at the starting Crit Damage of 1 doubles the hit exactly.

The damage a spell starts from is on each spell page. Spell Power and the other run stats are on the stat glossary, the crit step is on Critical hits, and the sigil and patient caster bonuses added in the spell step are on Sigils and casting.