Zvyth... the spell made to give one of your skeletal constructs an upgrade.

This spell reinforces the bones with extra ones increasing the skeletons physical ability scores such as con, dex, and str by 1 point at a time up to maximum of 20. (roll a d20 for proficiency the number needed to succeed will be up to the DM)

The skeletons bones are now dense enough they form a sort of bone armour around it from now whenever you use this spell and a maxed skeleton you will then increase its armour class by 1.

Max HP can be increased by 1 point per foe killed by the skeleton this spell is used on (the skeleton has to make the last hit).