I would not like to see any effect that forces a creature to use its own next action to move farther away... especially if the creature is slow (resulting in multiple turns to recover from the effect). If there were such a spell, however, it would have to be at least a level 3 spell, and cost on the order of 8-10 mana. (Mana cost is based on Turn to Stone at 2 +4 per turn, and Banish at 14 for three turns... the 0-2 mana reduction would be due to the creature's ability to do other things that might be useful, and due to the choice as to which zone it would move.)
Just on spells vs. undead:
It might be interesting to have a Holy spell that potentially(?) causes a "turned" condition on undead. This condition might essentially be a "stun" effect against undead... No move or attack, and remove after activation.
This might be an Incantation cast on the creature, an Equipment spell (Amulet?) allowing the wearer to "turn" undead (probably with mana cost based on level of creature), or a powerful Light-based attack spell that causes the condition in exchange for a lowered damage output.
An enchantment "Aura of Light" (or an Equipment spell providing such an aura) might be a damage barrier against undead creatures.
