Discussion of level 1 monsters.

Demons placed in free slots can annoy units with good spellcasting abilities but limited mana (devil, nightmare) and ruin the nerves of an average mage. Skeletons provide excellent cover for archers and mages thanks to their "bone-like" nature. In the late game, when all first-level units become roughly equal in strength, it's very useful to have leprechauns in a free slot to cast "Luck," which will boost more important units.