Kyton/Imp/Portal Encounter
I designed the Kyton to replace Longtail by doing several things. I lowered his SR to 12, made him vulnerable to silver weapons, made his control chains ability a move equivalent action, and then allowed him to control as many chains as he could see in a darkened room (60'R). I gave his control chain ability a +1 to hit bonus and 1d3 pts of damage per chain, then in every 5' square of the room I sunk 2 chains into the ceiling which hung down to within 3' of the floor. He had fast healing 5 which is strong against a low level group and prolonged the battle. With that I imposed a -2 to hit modifier upon every large weapon or missile weapon used in the room becouse of interferance with the chains. I was careful to describe the many razors and spikes set throughout the chains, and that the room stunk of carrion. Small bits of rotting flesh and wet blood caked the chains and from one was suspended RatTail's head, torn from his shoulders and pierced top to bottom with a spiked chain... goggles still on his head.
The floors all about were stained with wet blood and unreconizable chunks of flesh from many flayed victims.
Then I made the portal active. When the Kyton entered the room from RatTail's lair I made it pulse to the Devil's heartbeat, this was a clue to the players that it would stop being active if they could kill the devil. Then every d3 rounds it disgorged a menace. I varied the menace strength depending upon the fortunes of the players who were close to the portal. The first was a Darkmantle that gave those fighting near it severe headaches... then a rat swarm, then a Lemure, and finally a giant fiendish rat as the fighters there were being worn down.
Keep in mind that the party that fought this battle was 6 PC's strong and all were at level 2 (and they hit the room early, I had intended them to all be level 3). The biggest danger was the chain control. An unlucky PC, who didn't pay close attention to where he was fighting could be hit by 18 chain attacks (the square he was in, plus 2 in each surrounding squares). They figured out that by using a wall, and standing close together they minimized the number of these attacks they suffered. Even so, the wizard died to them. The Kyton had to keep moving to avoid being flanked, and even at 2nd level the PC's were inflicting serious harm upon it.
In the end they dropped the Kyton, finished off the last portal creature and had exhausted the Priests heal spells and all thier healing potions save one. I'd kept Achsyyx out of the battle for two reasons. One, because he would have tipped the scales and the party may all have died, and two because the Imp had direct orders to keep the portal open and so he stayed hidden (and thus alive) to watch over his charge.
I was later told that the fight recalled to some of the players a movie called Hellrazor. I don't watch horror flicks, and I was dissapointed a bit that the creativity of my encounter which I'd thought of as rather original and cool was used in a movie... but it was an intense and enjoyable fight regardless.