Ruined Rex kills Irelia with GA on Battlefield and Irelia kills Ruined Rex. Irelia has GA. When does damage for Ruined Rex get assigned, before or after GA? Can you not choose Irelia with Ruined Rex's Deathknell if you do not want to pay the Deflect cost?

In the scenario where Ruined Rex and Irelia (equipped with Guardian Angel) trade lethal damage during combat, the Guardian Angel replacement effect and the Deathknell ability behave according to the standard combat sequence.

The Short Answer

The Guardian Angel effect happens before the Deathknell damage is dealt.

According to the established RiftJudge FAQ (#10410, #10018), Deathknell triggers are placed on the chain when the unit dies, but their resolution is delayed until after the combat cleanup (which includes the healing step). Because Guardian Angel is a replacement effect that intercedes at the moment the unit would die, it triggers and resolves while the unit is still on the battlefield during the combat cleanup phase, before the Deathknell ability on the chain ever gets to resolve.

Step-by-Step Sequence

1. Combat Damage Step: Combat damage is dealt. Both Ruined Rex and Irelia are marked with lethal damage.
2. Triggering Deathknell: As Ruined Rex is marked with lethal damage and dies, its Deathknell ability triggers and is added to the chain as a pending item.
3. Replacement Effect (Guardian Angel): Because Irelia is also marked with lethal damage, the game attempts to process her death. Her Guardian Angel (a replacement effect) intercedes: it is destroyed, and Irelia is healed, exhausted, and recalled to your base.
4. Healing: Surviving units on the battlefield are healed (any marked damage is cleared).
5. Resolution: After healing is complete, the game proceeds to the FEPR (Finalize, Execute, Pass, Resolve) process, and the Deathknell trigger on the chain finally resolves.

Summary: By the time the Deathknell trigger resolves (Step 5), Irelia has already been saved by Guardian Angel and recalled to the base. If the Deathknell ability specifies "enemy unit here" (at the battlefield), it will miss its target because Irelia is no longer at the battlefield.

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