When does Sett's recall ability activate during combat, and does the recalled unit deal damage?

Ruling: Sett's recall ability activates during the damage assignment step after lethal damage is assigned to a unit with a buff, before damage is actually dealt. The recalled unit does not deal damage because it is removed before damage resolution.

Sequence:

• Go to damage assignment step
• Assign damage
• If lethal damage would be dealt to a unit with a buff, activate Sett's ability
• Recall the unit (before damage is dealt)
• The recalled unit deals no damage

Nuances:

• The ability cannot activate after a unit dies because you cannot activate abilities during cleanup
• The unit must have a buff for Sett's ability to trigger