Let’s come up with a monster.

I would add musketeers to the game. Ranged units with high damage output but low initiative (long reload time). Chance for a critical hit. If attacked in melee, they retreat without retaliating, but with increased initiative (a quick regrouping to fire at close range). We could also consider an ability where, when firing at close range, they can kill a number of creatures equal to the number of musketeers (I hope someone understands: all musketeers fire accurately and lethally at close range).