Ways to attack an enemy on a lower level?

[arlips]

I'm currently late in the game at the wormbound catacombs looking for one of the final two power gems. I'm stuck in the large rectangular room with a large basin with lots of zombies in it. You have to drop down, kill all the zombies and then activate the switches to open the gates to the power gem/exit. But there are a ton of zombies (like 7+) with no bottleneck point (no choice but to be surrounded), and they don't exactly die in one attack.

I'm not sure if any spells can do it, but I've been looking for ways to attack enemies on a lower level so I can soften up the crowd of zombies before dropping down. So far the only way I can see for doing this is to get really far from the enemy and throw something at it and hope the enemy is still in the square furthest away when the projectile arcs downward. But it's really hard here because it's very dark with no way to see if the enemy is still there.

Is there any way to attack an enemy right in front of you but on a lower level than you?

[minmay]

I'm stuck in the large rectangular room with a large basin with lots of zombies in it. You have to drop down, kill all the zombies and then activate the switches to open the gates to the power gem/exit.

No you don't. The lever that opens the teleporter is 2 spaces south of it. You can wait for those 3 squares to clear, then jump down and immediately pull the lever and teleport up. The undead will then go through the teleporter one by one and you can kill them normally.
Alternatively, use invisibility. Undead, like most other monsters, don't have see invisible, so they'll just stumble around ineffectually.

Is there any way to attack an enemy right in front of you but on a lower level than you?

Only the one you just described.

[arlips]

Oh, okay that will work too, thank you!

[Zo Kath Ra]

I've done it like this:
1) Pull the lever that raises the portcullis in front of the power gem
2) Take the power gem
3) Move onto the square where the power gem was

Now the party is protected by walls on three sides, and the zombies can only attack from one side.

[Dematto]

Forcefield (Concentrate 2) will allow you to temporarily create a bottleneck. Position yourself in a corner and cast it on one of the adjacent, open spaces to block that space off for a short time. If you have energy potions to spare, you can even weave in other spells. Forcefield. Fireburst. Forcefield.