When you cast this spell, you touch an unhatched egg and infuse it with necrotic energy. The life within the egg is accelerated, causing it to hatch prematurely. The creature that emerges from the egg is a full adult size horrifying undead version of what it would have naturally been. The selected creature type should be of CR 1 or less and should normally lay eggs (Basilisk, Griffon, Owlbear, Allosaurus, Ankheg, Ettercap, Gricks, Mimic, Plesiosaurus, Giant Snake, Spider, etc).

The undead creature uses the same stats as the base creature for everything, but its Intelligence, Wisdom, and Charisma scores are lowered to 6 respectively if they were higher. Its type changes to undead. It gains resistance to necrotic damage and immunity to poison damage and the poisoned condition. It also gains darkvision out to 60 feet if it didn’t have it already.

On each of your turns, you can use a bonus action to mentally command any creature you made with this spell if the creature is within 60 feet of you (if you control multiple creatures, you can command any or all of them at the same time, issuing the same command to each one). You decide what action the creature will take and where it will move during its next turn, or you can issue a general command, such as to guard a particular chamber or corridor. If you issue no commands, the creature only defends itself against hostile creatures. Once given an order, the creature continues to follow it until its task is complete.

The creature is under your control for 24 hours, after which it stops obeying any command you've given it. To maintain control of the creature for another 24 hours, you must cast this spell on the creature again before the current 24-hour period ends. This use of the spell reasserts your control over up to four creatures you have animated with this spell, rather than animating a new one.

At Higher Levels: When you cast this spell using a spell slot of 5th level or higher, the maximum CR of the creature you can affect increases by 1 for each slot level above 4th. And also, for each slot level above 4th, the duration extends by an additional 24 hours.