My players are becoming teleporting skirmishers.

So I have a group that is going to be level 8 in the next couple weeks or so and I love how they are working together to make encounters interactive.

Part of their process is that they like to teleport all over the battlefield with their powers. Swapping out characters who's turn is coming up and acting like a skirmishing swarm against my Monsters. There are also two players that have powers that attack monster Will and cause illusions.

I want to keep combat challenging without nerfing them. Any ideas on encounters or Monsters that would challenge a strategic teleporting party? I was thinking Monsters that either use teleportation themselves or who can become invisible. I was also thinking of Monsters that can dominate PCs.

Player list:
1 hamidryad Ardent/Bard hybrid
1 human sword mage
1 human monk
1 halfling warlock (fey pact)/rogue hybrid
1 human warlock (infernal pact) with a Dire Wolf companion

Well, first off, welcome to my Nightmare:P Also, do NOT think it will get better, either! But there are ways to challenge them. Here are a couple...

In the second Monster Vault, check the Goblinoids section. In particular, the Large sized Bugbear there. It has a very interesting Aura.

Make a Semi-Anti Magic Terrain that is a kind of Ward. It screws up Teleports in some way. For example, it could be One way, Meaning you can go into it but not out of it via Teleports or Vice versa. Or it could mess up the "Targeting" of the teleport, sending the creature to a random space adjacent to the intended space or 1d4 squares in a random direction. Don't over do this last one.

Also, I cannot stress the importance of Custom Monsters! I've got a handful that would be perfect for both examples and of about the right level for your game. I'll search for them and post them later on tonight after my Podcast Game.

GF

Terrain with lots of stuff that blocks line of site is good. Twisty maze like corridors filled with Brutes is good. Stuff that blinds. Enemies they can't see. Prepared actions can help. Lots of artillery might do you good in a wide open space., focus fire one player dead at a time. And of course teleporting and flying enemies. The one thing you won't be able to make a whole lot of use of are soldiers that do their thing by grabbing, immobilizing, punishing shifting ect.

One thing I would do is just have the enemies be a little smarter and realize that their typical tactics aren't working. Then have them fall back inside a building or something with windows for them to shoot out. Or retread and try lurkering the party.

Assuming the party isn't abusing dragonmarks and items then they probably made some serious tradeoffs for this. So any time they are in a poition where they are forced to just trade blow for bow they are the ones at a disadvantage.

Twisting corridors with Brutes might not be a bad idea. The group is in Baldur's Gate and I am going with adventures that allows them to get a better feel for the city. I was thinking about going into the Undercity for the next adventure storyline and Undercity would certainly fill that bill.

Well, this is all good advice and I can only reiterate a couple points.

1 - Terrain features are good! Confined space, blocking line of sight, and some "interfering magic" are all good ideas.

2 - See what the players "gave up" to become teleporting masters and give them some encounters that take advantage of that.

I also have to say that this was a great question and some great answers. I've seen (on other forum boards) DMs that will say, "My players are building uber-characters. How do I beat them?"

This thread is a nice change from that "DM vs Player" mindset. And I think that is awesome!

Remember that sight is required for teleportation. (I know I often forget this.)

Things to foil teleporting PCs (to use very sparingly, or when very story appropriate):
- darkness effects
- blinding effects
- wards (area non-teleportation zones)
- foes that stop teleportation (some githyanky have this - can be ported to other foes)

Things to "foil" PCs (also to be used sparingly)
- unstable reality/magic zones : damage on teleport, daze on teleport, became vulnerable x, etc
- slow IF the teleportation depend on character speed
- very short line-of-sight areas (such as twisting warrens, hedge mazes, brambles, etc.)
- fogs and such visibility reducing effects
- controllers that target actions
- soldiers with non-melee mark punishment

Things to reward teleporting PCs (this should be used often BUT see end note)
- nooks, crannies and ledges hard to access via other means
- "glass" and other line-of-sight-but-no-line-of-effect barriers
- grabbing creatures
- immobilizing traps and effects
- unstable hellfire-zones : damage to adjacent creatures on teleport, etc
- controllers that use slow, immobilize and zones to control the terrain
- soldiers with melee-based mark punishment

NOTE:
- when rewarding PCs in this manner (making them feel powerful by being able to "outmanoeuver" your encounters), it's important to remember to challenge them as well. This is easily done by upping the encounter budget - grant xp for a standard encounter, but add 2 standard foes to the mix. It's also important that, at least, some of the foes be able to still menace your PCs - simple ranged attacks fit this bill well.

When giving foes the ability to attack players at range when they otherwise should be more melee-focused, make sure to have the attacks be less impressive than what they would do in melee.

Final note
If you find that the teleportation is getting way out of hand, you can create something like the following action:
Teleportation Ward - Arcana (trained only) DC Hard (as a standard action), you create a burst 1 within 5 squares where teleportation is impossible until the end of your next turn.*

Make sure your players have access to this action and know of its existence. The goal is to have a open option that keeps the game tactical and allows for player agency.

*On second thought, having the ward require an Arcana check to teleport (DC = initial check) would probably be better. Failure could also still allow teleport, but deal damage, or daze, or etc. Or the zone could offer the choice : teleport and take damage OR try your skill and attempt to diffuse the ward and then teleport (much like a regular trap). Or something else, there are plenty of variants possible.