Giants

The Giants were a race of gigantic humanoids that lived in the land long before the events of Knighthood's history. They were known to possess unique magic and commune well with nature.

The red gems embedded in Gauntlets are made from the hearts of dead Giants, and their magic is what allows The Order of Rage to summon Heroes. Similar gems are found in the possession of Onslaught Dungeon Bosses, which may be what allows them to summon Monsters to their side.