Fusing monsters together will make them more powerful, increasing their attack, health and x stats. Fusion allows you to merge up to 5 monsters at a time in order to increase its level. Monsters that are the same element as the main monster offer more experience when fusing. Also, the higher the zone and rarity of a monster the more XP it will grant.
Fusion with special monsters
Special monsters are the elixir of the fusion world.