This spell merges two corporeal creatures of challenge rating 1 or lower into a single entity. Incorporeal and ethereal creatures cannot be merged by the use of this spell. You can shape the physical form of the new creature according to your wishes. For example, you could give it two heads, multiple arms, wings, or any other physical feature that the original creatures possessed.

The targeted creatures must be within range for the entirety of the spell. Unwilling creatures are entitled to a Constitution saving throw to resist the spell. If one or both of them succeed, the spell fails and has no effect.

The resulting creature possesses the cumulative hit points, abilities, and knowledge of its original forms. It retains any resistances, immunities, or vulnerabilities that either of the original creatures had. For instance, if one creature is immune to fire damage and the other is not, the resulting creature will still be immune to fire damage. Similarly, if one creature is vulnerable to a certain type of damage, this vulnerability will carry over to the merged creature. If there is a contradiction, such as one creature being immune to a type of damage and the other being vulnerable to it, the immunity would prevail.

To determine the alignment of the merged creature each creature make a Charisma saving throw. The creature with the higher result then determine the alignment of the merged entity. The most charismatic creature’s personality and beliefs becoming dominant in the fusion.

The effects of this spell are permanent once cast and can only be reversed by a Wish spell or similar potent magic.

At Higher Levels: When you cast this spell using a spell slot of 6th level or higher, the maximum CR of the creature you can affect increases by 1 for each slot level above 5th.

Example 1 - Merging a Rust Monster and a Quasit:

The Rust Monster has a rust metal ability, which corrodes nonmagical ferrous metal on touch. The Quasit has resistance to cold, fire, and lightning damage, as well as immunity to poison. When they are merged using the spell, the resulting creature would retain the rust metal ability from the Rust Monster and the resistances and immunity from the Quasit.

Example 2 - Merging a Cockatrice and a Pseudodragon:

The Cockatrice has the ability to petrify opponents with its bite. The Pseudodragon has resistance to magic, giving it advantage on saving throws against spells and other magical effects. When they are merged using the spell, the resulting creature would have the petrification ability of the Cockatrice and the magic resistance of the Pseudodragon.

Example 3 - Merging a Worg and a Hell Hound:

The Worg has keen hearing and smell, giving it advantage on Wisdom (Perception) checks that rely on hearing or smell. The Hell Hound has immunity to fire. When they are merged using the spell, the resulting creature would retain the keen hearing and smell from the Worg and the fire immunity from the Hell Hound.