Question: In our gaming group, our storyteller loves to use creatures with teleportation abilities. This is starting to get frustrating since as soon as a creature is bloodied, it teleports away with its next action. We've only managed to kill 1 creature in our last 10 combat encounters.

I'm looking for any powers or magical items that can prevent teleportation.

We do receive full experience for defeating the encounter. The issue is more the frustration of not actually killing the creatures, and that they keep coming back again and again.

Answer: 
I've attempted here to find some of the lowest level stuff that will do what you want, here's a couple of suggestions:

**Dimensional Warding - Swordmage Utility 6 - Daily**

It's a close burst 2 arcane/stance/zone that prevents teleport in or out.

[Dimensional Warding compendium entry](http://www.wizards.com/dndinsider/compendium/power.aspx?id=3358)

**Forbiddance Bolt - Level 9 Ammunition**

+2 ammunition that prevents teleportation.

[Forbiddance Bolt compendium entry](http://www.wizards.com/dndinsider/compendium/item.aspx?id=5234)

The bolts sound particularly handy as they can be used by anyone that can use a bolt!
Normal teleportation [requires line of sight](https://rpg.stackexchange.com/q/2238/8). So if you can break line of sight from a valid target space, you can prevent teleporation.

Some tactics and methods to accomplish that:

* make them blind.
* tactically use walls (like a `Wall of Fire`) to "box them in".
* immobilize them in a zone like that blocks line of sight (like `Stinking Cloud`).