Balrog

Magic weapon 3,
Add +4 Ac.
1d4 bludgeoning damage,
2d6 Fire damage.
For turn add 1d6 fire damage for atk
after first (max 3d6).
3 charge for long rest,
1 charge cost:
Str Save DC = player DC,
Melee atk + 10d6 fire damage
and go prone.