Undead Health Burst

Steadying yourself, you gain a necromantic facsimile of life, you heal 1d4 + 4 temporary hit points, until used up. 

You can't gain any other means of temporary hp whilst these are in affect. 

At Higher Levels: When you cast this spell using a spell slot of 2nd level or higher, you gain 5 additional temporary hit points for each slot level above 1st.