Let’s come up with a monster.

Exactly, like the fallen angels...
But that would create an imbalance... and there are already many unique features...

Now, also:
Visually, a mix of a cyclops (but with two eyes) and an Ent, like Gargantua from the fourth game.

Level 7 of the town is unknown.
Forest King
Health 250
Damage 50-77
Attack 25
Defense 40
Speed 4
Initiative 10
Abilities: Large creature. Elemental. Protects allies. Immune to Earth magic. Symbiosis. Area attack. Stun attack.
Vulnerable to fire. Regeneration on grass.
Cost 6000
Growth +1/Dwelling - Ancient Forest

In general, it attacks like a wild cyclops, stunning enemies and protecting allies from ranged attacks.