Animerge

This spell allows you to fuse two creatures together into one unique, amalgamated form, allowing a number of traits from each creature to remain dominant in its new singular form.

If you cast the spell on two creatures that have some magical adaptations, both targets must succeed on a Constitution save or die due to their conflicting innate magics. Otherwise the DM determines whether the creatures can be merged, if not the spell fails. A guideline for this is that neither creature can have magical adaptations.

You target two creatures that are within 20 feet of each other. The DM rolls 1d20 for both creatures, on a roll of 12 or higher the creature survives, if either dies the spell fails. If you attempt to merge opposing-blooded creatures (warmblooded birds and mammals vs. coldblooded reptiles and insects), they only survive on a roll of 8 or higher.

Should either creature have an Intelligence score of 5 or higher there is a 75% chance that the merged creature's mind will shatter, causing it to attack any creature it sees. Otherwise the DM determines creature's behavior.

The altered creature acquires the following basic traits from one or the other of the beasts involved in the merge: Body shape, size, movement modes, speed, diet, intelligence, attack modes, defense modes, special attacks, special defenses, and Armor Class. If you are a transmuter, you can request which traits are adopted in the new form; if not, the creature created is determined by the DM.