If a Stellacorn enters a battlefield that has no enemy presence, a showdown begins. Opponent uses a Wages into the Stellacorn. Stellacorn gets en garde to survive. Showdown ends, does it heal, or because there was no combat does it not heal?
To determine if your unit heals in this scenario, we must look at how Showdowns and combat resolution function.
The Short Answer
No, your Stellacorn will not heal.
The Rules Breakdown
- Non-Combat Showdown: Since there was no enemy presence on the battlefield when your Stellacorn moved there, this is a Non-Combat Showdown (Rule 459.2).
- Lack of Combat Cleanup: Healing in Riftbound—specifically the type of automatic healing you are asking about—is a feature of the Combat Special Cleanup (Rule 461.1.a), which occurs only during the Resolution Step of a combat showdown.
- Ending a Non-Combat Showdown: Because there was no combat ongoing, the Showdown concludes under Rule 348.2. When a Non-Combat Showdown ends, the game performs a standard cleanup, which does not include the "Heal all units" step found in combat resolution.
Summary
- En Garde: Your spell resolves as expected, granting your Stellacorn the temporary Might bonus to survive the damage dealt by your opponent's effect.
- Healing: Because this was a Non-Combat Showdown, the "Combat Special Cleanup" (which contains the healing effect) is never invoked. Your Stellacorn remains on the board with any damage it has marked on it (provided that damage does not equal or exceed its current Might).
This is my interpretation based on the rules for combat versus non-combat showdowns and their respective cleanup procedures. No official FAQ exists for this specific interaction.