The Deity Templar saps Isaac's stamina every time he summons a weapon..
[Ruler of the Deity Templar]
[Great Armory: A Mini World existing in a pocket space.]
-[Summoning a Weapon Consumes Stamina]
-[Weapons kept inside the Great Armory will be maintained. Unless it has been completely destroyed, it can be repaired to its perfect condition after some time.]
-[The Weapons in the Great Armory are kept at their highest form at all times.]
-[A Weapon on the attack cannot be called back to the Armory.]
-[The Great Armory can only store Weapons and Armors.]
-[Any Weapon registered to the Deity Templar cannot be replaced unless it is destroyed.]
-[Only one kind of each weapon can be kept.]
-[Only a corresponding attribute for each room can be stored.]
-[Weapons go back to the Armory after a certain distance or if rendered unconscious.]
These were the rules Isaac had compiled from using the Deity Templar Class.