Fusions is the event of two or more Ai or User's coding being spliced into each other, causing the Avatar to fuse into a new form. While most cannot bend coding to cause Fusions, various AIs have been programmed to purposely fuse with various others, or can have it bestowed or forced upon them.
There are many possible fusions, the currently recorded ones are:
Calirondus / Mariondus
The effect of a Fusion can result in various things, depending on those whom are formed. It could either combine their will, strength, and powers, or completely negate each other. While most powers that contradict, the fused avatars can find some ways to even improve on their powers using said contradictions, such as Calirondus' scoldering water.
But, in the best cases, the users powers are improved drastically, as well as their strength and size. While the Fusion is controlled with will, and whoever has the strongest will can easily fight the other mind, they are both mentally active, so mental and physical traits of both avatars can be expressed. Fusions can be split if they become too emotionally or mentally conflicted, or damaged significantly.