Does absorb prevent damage or reduce it before it's dealt?

Absorb is a static ability that reduces the amount of damage a source would deal, as defined in CR 702.64. When a source with Absorb N would deal damage, that damage is reduced by N before it is dealt. This means the damage event itself is smaller — not that damage is dealt and then prevented afterward.

This is a subtle but important distinction from prevention effects (like a damage prevention shield). Prevention effects use the damage prevention step during combat damage assignment (CR 510.4) and are processed differently. Absorb, by contrast, modifies the damage value as part of determining how much damage is dealt in the first place.

Practically speaking, the outcome is similar — less damage gets through — but the mechanism matters for interactions. For example, if an effect says 'whenever damage is dealt to this creature,' Absorb could reduce that damage to zero, meaning no damage is 'dealt' at all, and the triggered ability would not trigger. A prevention effect that reduced damage to zero after it was 'dealt' might interact differently depending on the exact wording.

Concrete example: Your creature has Absorb 2 (like Wizened Cenn or a creature enchanted appropriately). An opponent's spell deals 3 damage to it. Instead of 3 damage being dealt, only 1 damage is dealt. Your creature takes 1 damage, not 3 — the event never involved 3 damage reaching it.

Because Absorb reduces damage rather than preventing it, effects that replace or respond to damage being 'dealt' see only the reduced amount (or nothing, if Absorb reduces it to zero). See CR 702.64a for the full rule text on Absorb.