When Ekko Recurrent dies in combat, do you recycle him and ready your runes before combat cleanup, and can you use those runes to finish off damaged units?

Ruling: You cannot use the readied runes to deal further damage to units damaged in combat. Deathknell resolves after combat cleanup.

Sequence:

• Combat damage is dealt
• Combat cleanup occurs (damaged units heal)
• Deathknell triggers and resolves (Ekko is recycled and runes ready)
• No reaction window exists after Deathknell to use the readied runes

Nuances:

• The rules as written don't perfectly match this intended timing, but the FAQ on Kog'Maw clarifies that Deathknell resolves after combat cleanup