Bolster Undead

Using your knowledge of undead you can use necromancy magic to improve a undead servant.

You may not use this spell twice on a single undead until the original effect has ended.

you target one undead creature under your control that you can touch, doing so immediately grants the undead 3d6 temporary hitpoints, (if the undead is injured you heal 3d6 hitpoints any excess are turned into temporary hitpoints. e.g. If the undead creature you target has a hitpoint maximum of 20 and has taken 10 damage, after casting the spell on the undead you roll 13 you then heal 10 hitpoints taking it to 20 hitpoints and the remaining 3 are converted into temporary hitpoints).

 After which a secondary effect occurs depending on the undead:

Zombie: Gains an additional d6 of temporary hitpoints (rules described above). Furthermore its “undead fortitude” ability is changed to,  “if damage reduces the zombie to 0 hitpoints, it must make a constitution saving throw with a DC of 1, plus the damage taken, unless the damage is from a critical hit. On a success the zombie drops to 10 hit points instead.”

Skeleton: Remove bludgeoning as a damage vulnerability, additionally any attack made by a skeleton, (with a weapon or without) does an additional 1d12 of necrotic damage.

Ghoul/Ghast: select one of the following, slash, bludgeoning or piercing. Depending on which you chose it gains resistance against that type of damage (even if the attack is magical). Furthermore you can increase the Ghouls/Ghasts movement by 5ft, additionally you may mark a target in which case you can choose to give the Ghoul/Ghast either advantage on its next two attack rolls against the target or to give the target disadvantage twice when attacking the Ghoul/Ghast.

Wight: Remove the “Sunlight Sensitivity” ability, additionally a dark breastplate forms on the Wight causing it to gain the benefits (and downsides of wearing one) turning its AC into 16, Furthermore it adds 3d8 necrotic damage to its attacks (with a weapon or without), in addition its life drain ability can now be used as a bonus action.

Mummy: increase its AC to 15, it also loses its vulnerability to fire damage, furthermore increase its movement by 10ft, additionally increase its DC for it’s “dreadful glare” ability to DC 15.

Should you use this spell on a living creature nothing occurs.