Necrotheurgist

Prerequisites: School of Necromancy and proficiency in Arcana 

Benefit: You can imprison animated or created undead you've created with a spell within a gemstone, allowing you to recall them later. When you maintain control with the Animated Dead or Create Undead spells, you can choose to store the undead instead within a gemstone of your choice instead of having it remain in your immediate vicinity.

Gemstone Requirements: The gemstone must be in your possession when you maintain control of the undead and must be worth at least 100gp per spell slot level used to cast the spell.

Release Undead: You can recall the undead creatures from a gemstone as a bonus action on your turn. The recalled creatures are restored to their full hit points and are in the same condition as when they were stored in the gemstone. The released creatures must appear within 30 ft. Of the caster. You must make a successful DC 5 Arcana skill check each time you release the imprisoned undead or the gemstone is destroyed. Each time you use a gemstone in this manner, the DC increases by 5.

Limitations: You can only store one spell's undead per gemstone. If you attempt to store other animated creatures in a gemstone that already contains some, the spell fails and any imprisoned undead are lost.

Design Notes: This feat is designed to provide a solution for necromancers who want to create and control large numbers of undead creatures without having to worry about them wandering off or getting in the way. It allows them to store their animated dead in a convenient and accessible way, making it easier to manage their undead minions. The feat's limitations ensure that necromancers still have to make strategic decisions about how they use their abilities, rather than simply being able to store an unlimited number of creatures.