If a ruined Rex dies in combat to a unit with 10 might, does the ruined Rex apply its 6 damage and then the deathknell 4 damage on top of it before the unit heals? Essentially killing the unit?
No, Ruined Rex's Deathknell ability will not kill the enemy unit in this scenario. According to the official rules and RiftJudge FAQs, the healing step occurs before the Deathknell damage is dealt.
Here is the step-by-step combat sequence:
- Combat Damage Step: Combat damage is dealt. Your Ruined Rex (6 Might) and the enemy unit (10 Might) deal damage to each other. Ruined Rex is marked with 10 damage and dies.
- Triggering Deathknell: As Ruined Rex dies, his Deathknell ability triggers and is added to the chain as a pending item (Rule 428.1.a.1.b).
- Killing Units: Ruined Rex is moved to the trash.
- Healing: Surviving units on the battlefield (including the enemy unit that killed your Rex) are healed (Rule 461.1.a.1). Any damage marked on that unit is cleared.
- Resolution: After healing is complete, the game proceeds to the FEPR (Finalize, Execute, Pass, Resolve) process, and the pending Deathknell trigger on the chain resolves, dealing 4 damage to the target.
Because the enemy unit is healed in step 4, the 10 damage it received from Ruined Rex during the Combat Damage Step is removed before the 4 damage from the Deathknell is applied in step 5.
Sources: RiftJudge FAQ #10090, FAQ #10018, and FAQ #10069.