If I react with sacrifice on a unit targeted by Mirror Image, does it work?

Question

Accepted Answer

To determine if you can react with **Sacrifice** on a unit targeted by **Mirror Image**, we must look at the timing of these cards and the requirements for playing them.

### The Ruling
**Yes, you can play Sacrifice in response to Mirror Image.**

Because **Mirror Image** is a spell, it uses the chain. When your opponent plays **Mirror Image**, it is placed on the chain, and you receive priority to play a [Reaction] (or an [Action] if the state were open, but playing a spell from the hand usually happens in an open state, and your reaction would then close it). **Sacrifice** has the [Reaction] keyword, which allows it to be played during a closed state (while the chain is not empty).

### Important Considerations
While you can play **Sacrifice** in response to **Mirror Image**, there are two critical factors to keep in mind:

1.  **The Cost of Sacrifice:** **Sacrifice** has an additional cost: *"Kill a friendly [Mighty] unit."* You must be able to pay this cost at the moment you play **Sacrifice**. If you do not have a friendly unit with 5+ Might to kill, you cannot play **Sacrifice**.
2.  **Mirror Image's Target:** **Mirror Image** does not target the unit until it resolves. When you play **Sacrifice** in response to **Mirror Image**, the **Mirror Image** spell is still on the chain and has not yet resolved. Therefore, the "copy" has not been created yet. 
    *   If your goal is to kill the unit that **Mirror Image** is targeting to prevent the copy from being created, **this will not work**. **Mirror Image** will still resolve; if the chosen unit is no longer on the board (because you killed it for **Sacrifice**), the instruction to copy it will simply fail to execute (Rule 359.3.e.6), but the spell itself will still resolve.

### Sequence of Events
1.  **Opponent** plays **Mirror Image** (choosing a target). It goes on the chain.
2.  **You** play **Sacrifice** as a [Reaction].
3.  **You** pay the cost for **Sacrifice** (kill a friendly Mighty unit).
4.  **Sacrifice** is finalized and added to the top of the chain.
5.  **Sacrifice** resolves: You draw 2 cards and channel 1 rune.
6.  **Mirror Image** resolves: It attempts to copy the chosen unit. If that unit is no longer on the board, the instruction is ignored (Rule 359.3.e.6).

This interpretation is based on the standard chain and timing rules (Rule 359.3). No official FAQ exists for this specific interaction.