Hezrou as a boss battle

[Braininthejar]

How to handle the big toad? (as a boss battle, meaning he is still higher level than the party)

Between his stench and blasphemy he pretty much disables close combat attackers. His SR will block more than half the spells and spell vulnerability is "fortitude negates".

So, apart from summoning evil/poison resistant monsters, what would be your way of tackling him?

[sirpercival]

Silence takes out Blasphemy.

[Braininthejar]

If cast at a point in space it bypasses the will save and SR but will only stop him for one round since it doeasn't stop teleporting
 Will require an anchor spell...

Anything more?

[Braininthejar]

I finally found it.

1 neutralise poison grants immunity for a time, allowing the fighty types to actually swing at the thing.

2 orb of force.

[RobbyPants]

What level is the group?

If you don't stop it from teleporting, you have to take it out in a single round before it acts. You already mentioned the poison immunity part (heck, Delay Poison can work for the battle, even).

Heck, two 6th level pounce chargers each with potions of Delay Poison could probably take him out on the first round.

[Braininthejar]

If he is forced to teleport away, they will probably lose him. Its not like he can go to town and ask for directions. 

[Quillwraith]

Does he want to teleport away?
If it looks like he's winning until they kill him, he might not.
If they have something he needs, he might not.
If he needs to kill them, he might not.

[RobbyPants]

If he is forced to teleport away, they will probably lose him. Its not like he can go to town and ask for directions. 

Yeah, that's why I said:

If you don't stop it from teleporting, you have to take it out in a single round before it acts.

So your the two options are removing its teleport ability on round 1, or making it so it can't act on round 1.

[Braininthejar]

He was forced to sign up to kill them through planar binding.

[Bauglir]

So, he'll be back if he flees, you say. And the party may be able to arrange to face him on their terms.

EDIT: See if you can't cut a deal. Buy a scroll of miracle or something, free it from service.

[phaedrusxy]

If cast at a point in space it bypasses the will save and SR but will only stop him for one round since it doeasn't stop teleporting
 Will require an anchor spell...

Anything more?

You don't cast it on a point in space, or on an enemy (ever). You cast it on an amulet or something else you can put in your pocket/inside your shirt (to block Line of Effect) when you don't want it, and pull it out when you do.