Collars are weapon Items, they allow for Players to Tame NPC monsters and allow them to sue them in battle two ways.
1. Collar equipped as Sub-equip, Monster will appear and allow user to control monster to attack with both character and Monster and Monster retains all its stats that it had when it was tamed.
2. Fusion, when collar is equipped as Sub-weapon players can dismiss monster to equip to main weapon. By doing this Player will gain the Atk and def of tamed monster, and also be able to use monster's attacks but will drain SP by 70 each Monster attack used. When this happens Sub equip weapon is left empty.