Spoiler: Battle Map
1 W W W W W W W W
2 W W W W W W W W
3 W W P P P W
4 W P P P W
5 W W
6 W W
7 W P P O O O W W
8 W P P O O O W
9 W W O O O W
10 W S P M W W
11 W P P P P W
12 W P Ma Ma P P P P P W
13 W Ma Ma P P P P W
14 W TT P P W
15 W W P W
16 W P P W W
17 W P P P W W W
18 W W G G G G G G G G G G G W W
19 W W W G G G G G G G G G G W W
20 W W W W G G G G G G G W W W W
W = Walls.
P = Pillar. Does not extend all the way to the ceiling but at least 15 feet high and near impossible to stand on.

M = Malog.
Ma = Marambe.
TT = Tsu-Tze.
S = Serafino.
G = Goblin.

O = Ooze.

Will update when I know how everyone responds to the trample.

Spoiler: Knowledge: Dungeoneering
What has entered this dungeon is something alien indeed. The black mass is an extremely rare creature known as a Shoggoth. They don't do much except eat, but that one thing they are extremely proficient at. They employ a strategy of mass destruction, trampling everything in their path rather than focusing on one opponent at a time, and swallowing any creatures that don't get out of the way.

Their liquid flesh make them very difficult to injure - the easiest way to damage it is to allow it to swallow you and attack it from within, however that also involves taking damage from its strong acid and violent stomach movements (and teeth). It has a piercing scream that drives most creatures mad, causing them to mistake allies for foes and quickly damaging their mind over time. It has resistances to most energy types, to spells and to physical attacks. It can't fly, but it can move as easily on walls and ceilings as on the ground and underwater.

It's, uh, it's not really an enemy you can defeat by throwing goblins at it. It doesn't have any disintegration like abilities, so it probably killed and ate the Kraken and the Drow on its way down here.

It likely can't take as much damage as the Kraken, but it will be dishing it out much faster in return. Its main weakness is probably that, not being very intelligent, it will almost always try to eat as many creatures as it can, rather than focus fire against a single threat at a time.

Tsu-Tze's rock bounces harmlessly off the liquid flesh of the ooze, and as it rolls off the creature probes it with tongues and teeth, discarding it as uninteresting.

Serafino's slam connects well enough, although the ooze does seem to have resisted some of the damage. He did successfully steal some of its life energy, however.

Teeth and eyes roll out in a horrid mass to swallow Malog. It is not a slam or a grapple, it rolls over the warleader, then reverses direction, rolling over the space of Serafino, then on to Marambe and finally Tsu-Tze in one terrible movement. In the precious seconds this takes, each of its victims faces a choice. You can make an attack of opportunity, or you can make a reflex save to avoid being crushed. If you fail that save or you take the attack of opportunity, those mouths will be trying to swallow you whole.

Spoiler: Trample
Can't really roll for you on this one, since everyone needs to decide whether to go for the free attack or try to not get eaten.

Spoiler: Marambe
Since you readied an action to attack if it got in range, you get to make that attack and either make an attack of opportunity or make a reflex save. It is Huge, you are Large - it is possible for you to bull rush it. However, it resists the bull rush from your readied action. It does take damage from the attack, though.