So, if there was anything that Yveric knew prior to his death, he wouldn't know it anymore, nor could he tell anyone about it.
And usually, Kraymar renamed his Undead, but he allowed Yveric to keep his name as a result of Vellamira's request before they came here.
While Yveric would remember his loyalty to the Wargraves, he wouldn't be able to act on it because, at the moment, his loyalty now lay with his Master, Kraymar.
Kraymar's ability was capable of twisting an Undead's loyalty towards him. After all, if the ability couldn't do this, what was the use of resurrecting someone who was just going to attack you?
Another limitation of his ability was Will, which was the most important factor. If the dead possessed an insanely strong Will that was almost as strong as, equally strong as, or stronger than his own Will, his ability would fail.
