GM: Given that 5 of you were nearly defeated by the first encounter, you can make a reasonable threat assessment that whatever's deeper in there is likely to be bad news. However Dunstan with his knowledge of dwarven crafting can tell that the lintel of the door you entered the well room by could be brought down, triggering a collapse that should block whatever evil lurks down there awhile, hopefully until after the wedding...
You break the door lintel at Dunstan's instruction and make a hurried exit from the Hall of Echoing Screams as rocks fall behind you, leaving Adakmi with the lower vaults sealed off (for now) and taking the body of Jareth's fallen soldier for burial (he can't be Raised). Back in Northwood a couple days before the wedding, and the guests are due to start arriving tomorrow, when you get a message from Halvath the Green Regent asking if his old friends could help him deal with something - river merchants report evil-looking yellow humanoids spotted in the ruins of Zelbross, and one of Halvath's more senior Needles, Valdrin the Wanderer, assigned to scout the area is missing. Normally the Regent would send more Needles & Shadoweir to deal with a likely goblinoid incursion, but something gave Halvath a bad feeling about this. He made some consultations, and Curuvar the Brazen of Loudwater believes the creatures could be Githyanki, legendary 'star pirates' of considerable power, and that this could be a Githyanki scouting party preparing the way for an invasion! If so, they need to be dealt with right away.
19/6/81: Dunstan Paelias & Jareth travel to Loudwater, where Brikos Stoneshoulder is unveiling his new statue of "Quinn atop the head of Emerald Dawn" in the town square. From there riding west to Brownstone and consultation with Halvath, then on to the ruins of Zelbross. Paelias tracks the raiders to hidden chambers beneath the ruined Temple of Tyr. Most of the Githyanki cadre prove little threat, but they are opening a portal to their home realm that will allow an army through. Fighting to close the portal, Paelias is scorched by the magic of the Gish sword-mage leading the squadron, but Jareth gets him back on his feet and the group are at last victorious, killing the Gish and closing the portal. Too bad there's no treasure... except a big pile of everburning torches.
The trio return to Loudwater that night with Bags of Holding bulging...
By Githyanki: 1 Needle of the Regent, Valdrin the Wanderer, was killed by Githyanki two days previously.
10 Githyanki Warriors
3 Githyanki Corsairs, "arrr"
1 Githyanki Mindslicer
1 Githyanki Gish
1 Mulch Roper
3 Redspawn Firebelchers
Combat XP 16300/3=5466 each
Level 13 Major Quest - close Githyanki Portal: 800 each
Total: 6266+ 94,600=100866
Need 99,000 for 18th level
LEVEL 18 REACHED
Need 119,000 for 19th level