My DM told me if you command undead as an evil cleric, and relinquish command of them later, they just stand around -- they don't go back to the control of whoever commanded them before. True?
In his game the answer is yes.
But I believe it is also true per the RAW.
When command is relinquished they go back to their "natural" behavior.
Now the big question is, what is their "natural" behavior?
Well it's my belief that they would just go back to attacking the next thing that moves close.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.