[ Here's a example of a fusion above ]
Scenario 1- You and your crush where on a mission to gather materials for slenderman when you stumbled across a odd gem stone you touched it and showed it to your crush but when they all touched it surrounded you two with a bright light and before you knew it you had just fused with your crush!

Scenario 2- Slenderman has had enough of you and the person you hated fighting all the time so he grabbed a odd gem and while the two of you where fighting he threw it at you and when you two got close enough it out up and fused you and them together

Scenario 3- make your own up