Class

Priest

Salvation · levels at 2 / 4 different pieces

Every Priest piece: Priests can't be mind controlled.

A piece's level is its cost, +2 for each extra star (★★★ 5-cost = level 9).

2
When you lose a round, take damage and survive while you have an empty board slot, you get a Tango (restores 1-8 courier HP).
4
At battle start, one Priest per empty board slot (highest level first) mind controls the highest-level enemy at or below its own level. The control lasts (Priest level x 2 + 1) seconds and ends early if the Priest dies.
Note: The tooltip doesn't mention that invisible enemies and Tidehunter can't be controlled, or that targeting an enemy Priest wastes the attempt.

Official in-game tooltip

Priest Pieces are determined, and cannot be mind controlled.
Class Perk: Salvation
Active when you have at least (N) different Priest pieces on board. (Multiple effects stack)

(2) Priests: Get a Tango when defeated in a home battle with courier health lost if your pieces on board are less than your max pieces capacity.
(4) Priest: Every Priest piece will Mind Control an enemy whose level equals to or less than itself if your pieces on board are less than your max pieces capacity. (Max control count = Your capacity - Your pieces on board)

Priests are blessed invokers of light and darkness, who express their determined spirits through dedicated service to the people. For numerous battles, with the mastery of light and shadow energies they have weaved the most reliable life-saving protections for their allies.