THINGS THAT HAPPENED WHEN MY PLAYERS WENT THROUGH THIS MONTHS AGO
The players chopped at the phalanx slime and ultimately decided it was better to just hold it off by having someone with a polearm do a 'fighting retreat' so that everyone else could move around the top floor without getting cornered. That player ended up learning phalanx fighting-style from his efforts, allowing him to give his shield defense to adjacent allies or get an extra +1 AC if both he and the ally had shields and fought in formation. I forgot the doors to 2 and 3 were locked and had the mimic chest run around at unarmored human speeds and dive down the central pit on the top floor to lure people into the Benthic Chimerae pool and generally be a goofy chase scene, though the pursuing elf getting eaten by the Chimera and managing to stab its eyeball before perishing alone was less goofy. The axe Grafter was a very popular item for the rest of the campaign, though obtaining it was awfully easy because I let a hafling get into the room when I had meant for shrinking down to itty-bitty size via Pachama's spells or potions or the polymorph pearl to be necessary to retrieve the mighty weapon. Pachama was put to Sleep and carried in a backpack of a player who then received the Ur-Chimerae's Blessing and fused with the carried Pachama and became a spider-halfling with a vestigial spider-wizard brain inside them that could cast spells. Pachama briefly took over the halfling's body later.
After the Ur-Chimera was slain (at great loss of PC life) only some of the treasure could be taken, and a sunken ship pulled by an Aboleth and crewed by its Skum minions showed up from the Undersea to investigate the ringing bell to repopulate the dungeon and haul off a lot of platinum before spider-halfling player came back to finish looting the place. The skeleton fighter player who accompanied the sneaky noncombatant for visit #2 held off a great many Skum single handedly in the chokepoint of the staircase, acting as a distraction. Skum attempting to kill him with burning oil ended up doing more damage to themselves than him. The thief chose to kill some Skum instead of sneak by and take loot bloodlessly, and questioned his own morality when he realized that his slaughter was unnecessary. The fighter fulfilled the required feat of daring, holding off 20+ enemies at a chokepoint, to receive training from Royal Guard Dnorr and was less conflicted.