If I have a buffed mighty unit, can I use Sacrifice then protect it with Sett the Boss? Will I still draw and channel if so?

Yes, you can do this, and yes, you will still draw 2 cards and channel 1 rune.

How it works

This interaction works because Sacrifice has a "kill" instruction as an additional cost, and The Boss's ability is a replacement effect that modifies that event.

1. Playing Sacrifice: You play Sacrifice and choose your buffed [Mighty] unit to kill as the additional cost.
2. Paying Costs: During step 4 of playing a card, you attempt to pay the cost by killing the unit.
3. Replacement: The Boss's replacement effect intercedes. Instead of the unit being sent to the trash (killed), it is healed, exhausted, and recalled to your base. The buff is spent as part of this effect.
4. Cost Completion: According to Rule 357.2.a, costs that are replaced by a replacement effect are still considered successfully paid.
5. Resolution: Because the cost is considered paid, Sacrifice finishes resolving normally. You draw 2 cards and channel 1 rune.

Important Notes

• Replacement, Not Trigger: The Boss's ability is a replacement effect, not a triggered ability. It does not go on the chain and cannot be responded to by your opponent once you pay the [C] cost (FAQ #5828).
• Buff Spent: As part of the resolution of The Boss's ability, your unit's buff is removed (spent) (FAQ #5629).
• Consistency: This is consistent with FAQ #10281, which clarifies that costs replaced by similar effects (like Tactical Retreat) still allow the spell/ability to resolve fully.