Luthien Isilme Di'Aegnor

When Luthien Isilme Di'Aegnor enters the battlefield. Target opponent becomes the monarch.
You can't become the monarch this turn.

If damage would be dealt to Luthien Isilme
Di'Aegnor while you're the monarch, prevent that
damage and put that many +1/+1 counters on it.

—
"Regent by Birthright, Ruler by Action."