Fire Elemental:

 

 
banishing item - Neptune's Horn
reward - 600 coins, 6 Energy Points, and a Fire Guardian Chest.

 

Werewolf Leader: 

 

banishing item - Silver Fang
reward - 600 coins, 6 Energy Points, and a Full Moon Chest.

 

Clot of Dark: 

 

banishing item - Greek Fire
reward - 600 coins, 6 Energy Points, and a Dark Servants' Chest.

 

Gremlin Leader: 

 

banishing item - Web of Lightning
reward - 600 coins, 6 Energy Points, and a Gremlin Chest.

 

Medusa: 

 

banishing item - Mirror Shield
reward - 600 coins, 6 Energy Points, and a Medusa Chest.