Can I reveal a hidden Evelyn at a battlefield after my opponent plays Ruination and keep control of the battlefield?
Whether you can keep control of the battlefield depends on the state of the battlefield at the moment The Ruination resolves.
Here is the breakdown of how this interaction works:
1. Timing and Control
- The Chain: When you play The Ruination, it is placed on the chain. Because there is an item on the chain, control of the battlefield cannot be lost while the chain is active (Rule 187.4.c, Unleashed update).
- Revealing Evelynn: You may reveal your hidden Evelynn, Entrancing in response to The Ruination. Since Evelynn is hidden, she gains the [Reaction] keyword (Rule 811.6), allowing you to play her while the chain is closed.
- Resolution: Items on the chain resolve in Last-In, First-Out (LIFO) order. If you reveal Evelynn after The Ruination has been played, Evelynn enters the battlefield, and her "When you play me from face down" triggered ability is placed on top of The Ruination on the chain.
2. Can you keep control?
Whether you keep control depends on the board state after The Ruination resolves:
- The Chain Resolves:
- Evelynn's trigger resolves first. If you have a target, you may move an enemy unit to her battlefield.
- The Ruination resolves next, killing all units on the battlefield (including Evelynn and any unit you moved).
- Post-Resolution Cleanup:
- Once the chain is empty and all effects have resolved, the game checks for battlefield control.
- According to Rule 461.5, if there are no units remaining at that battlefield, it becomes uncontrolled.
- Crucially: Even if you play Evelynn in response, The Ruination kills all units on the board. Because Evelynn will be killed by The Ruination, you will have no units remaining on the battlefield when the spell finishes resolving.
Conclusion: You cannot keep control of the battlefield. While revealing Evelynn is a legal play, The Ruination will kill Evelynn as part of its resolution, leaving the battlefield empty and thus uncontrolled.