If you use sacrifice on a unit with deathknell, can you stack the trigger? Or do they go off in a specific order?

When you use Sacrifice to kill a friendly unit that has a Deathknell ability, the effects do not "stack" into a single combined trigger. Instead, they are processed as two separate events that are placed on the chain.

According to the rules and related FAQs (specifically RiftJudge FAQ #9787), here is the breakdown of how the sequence works:

The Sequence of Events:

1. Playing the Spell: You announce Sacrifice and choose your Mighty unit as the target to satisfy the "kill" cost.
2. Paying the Cost: You kill your unit. This action fulfills the requirement for the spell, and simultaneously triggers the unit's Deathknell ability.
3. Deathknell as Pending: Because the unit was killed, its Deathknell trigger is created. Per Rule 808.1.d.2, it is added to the chain as a Pending Item.
4. Resolution of Sacrifice: Sacrifice finishes its resolution: you draw 2 cards and channel 1 rune.
5. Finalization: With Sacrifice now fully resolved, the game moves to the Finalize step. The pending Deathknell trigger finalizes and is placed onto the chain as a standard chain item.
6. Resolution of Deathknell: You now have priority to resolve the Deathknell trigger.

Summary

You cannot change the order of these two specific events: you will always draw the cards from Sacrifice before the Deathknell ability resolves.

• Rule Reference: Per Rule 808.1.d.2, the Deathknell trigger is added as a pending item the moment the unit is killed as a cost. It cannot be placed on the chain until the spell currently being resolved (the one that triggered the death) has finished its resolution.
• FAQ Reference: This interaction is explicitly confirmed in RiftJudge FAQ #9787, which clarifies that triggers resulting from costs paid for a spell are treated as pending and only resolve after the spell has completed its effect.