So the troll was really a corpse like i thought. Now it is interesting why it was the only undead in the attacking group fr the test or if the goblins did not notice it on the other attackers.
@Abetillo: I know it's been a while but did you forget the previous chapters? Ainz himself killed and turned it undead. Then ordered it to command the attack the village, so they could get the magic sword. It was originally one of the "four kings" of the forest so it could obviously order other monsters around.