Beings of Tash Kalar
You can see a bulky lump of meat. Or stone. Or whatever is troll made of.
This is not a blind destruction, the troll picks only enemy tokens (and only the weak ones) – and eats them. If enough tokens is eaten, you gain energy for one extra action.
Mountain troll is one of my favorite beings, as using it well feels very rewarding. Its pattern is not difficult, and it is usually worth to spend some time to prepare it at a right place, as you gain one action back then. However, sometimes it may be so difficult it is better just summon it without gaining the extra action.
The original effect didn't have that extra action, and before Troll inherited it, it belonged to Champion. However, both that old Champion and the Mountain Troll were rather weak beings - the time has shown that destroying all adjacent enemy commons is not as good as it looked, and it is usually not worth the effort to summon the being at a space closer to enemy common pieces. That's why I added an extra reward for good summoning.