Madstone

From BoardGameGeek:

Wizards and creatures wander a dark land where only the strongest survive and amass large, powerful armies to conquer. Madstone is a card game with power crystals that are collected by players to either capture or kill creatures and warriors. Capturing them adds power as they join your army. Killing them gives victory points. The strategy comes into play as each player decides when to kill and when to capture. Players can attempt to kill or capture other players' armies, but only when darkness falls. The game ends when the deck is exhausted, the player with the most points showing on killed creatures is the winner.