Can I use Sacrifice on a unit that got targeted by a Tactical Retreat earlier and get full value from it?
Yes, you can use Sacrifice on a unit already targeted by Tactical Retreat, and you will receive full value from the spell.
According to RiftJudge FAQ #9425, this interaction allows you to satisfy the cost of Sacrifice while keeping your unit on the board.
Sequence of Events
- Preparation: A friendly [Mighty] unit is already under the replacement effect of Tactical Retreat (meaning the next time it would die this turn, it will be healed, exhausted, and recalled to your base instead).
- Playing the Spell: You play Sacrifice and choose that Mighty unit as the target for the additional cost: "kill a friendly [Mighty] unit."
- Paying Costs: You attempt to pay the cost by killing the unit.
- Replacement: The replacement effect from Tactical Retreat intercedes. Instead of being sent to the trash, the unit is healed, exhausted, and recalled to your base.
- Cost Completion: Per Rule 357.2.a, costs replaced by replacement effects are still considered paid. Your cost is successfully paid.
- Resolution: Sacrifice resolves normally. You draw 2 cards and channel 1 rune.
Summary: You get the full effect of Sacrifice (draw 2 cards, channel 1 rune), and your unit survives the cost payment by being recalled to your base instead of being killed.