Consume Essence

You conduct a grisly ritual to imbue one creature with the aspects of another. At the end of the spell's casting time, one willing creature you touch can consume the heart used in the spell's casting. Immediately after the casting of the spell, and then every day at dawn for the duration, they gain temporary hit points equal to the challenge rating of the creature whose heart was used in the casting of the spell. In addition, for the duration of the spell, they gain an aspect of your choice from the creature whose heart was consumed in the casting. This aspect can be any one of the following options:

All of the creature's speeds, such as flying, swimming, or burrowing. If they gain a swimming speed, they also gain the ability to breathe both air and water.

All of the creature's special senses, such as tremorsense or blindsight

The creature's natural armor trait, if it has one. If the target of this spell gains natural armor, their armor class is calculated as the creature's armor class minus the creature's dexterity modifier, plus the target's dexterity modifier.

Any one of the creature's special traits, such as the Remorhaz's heated body trait or the Storm Giant's innate spellcasting trait. The target cannot gain any ability listed in the creature's action list, such as the Mindflayer's mind blast action.

Due to the complex nature of intertwining the essences of two creatures, any creature who benefits from this spell cannot benefit from it again during its duration. In addition, if you cast this spell a second time during its duration, any creature benefiting from the first casting of the spell loses the benefits immediately. 

At higher levels:

When you cast this spell using an 8th level spell slot, its duration is 1 week. If you cast it using a 9th level spell slot, its duration is 1 month.