Gossamer Crypt is the Gilded dungeon in Skittering Precinct for Night Market. Gilded Alziriix is the only boss.
Do not let Spider-Kith Horde-Menders heal Alziriix. Get out fast after Daedric Explosion. Kill Hoarvors and throw a sac at the boss to unenrage it.
Daedric Explosion pulls everyone in with Grappling Web and then blows up around Alziriix, so get out fast. Spider-Kith Horde-Menders can heal the boss if you do not interrupt them, while Call Lightning keeps the floor moving.
Alziriix periodically enrages . Keep an eye out for hoarvors so you have sacs ready when that happens.
pull and then AOE explosion around the boss
Daedric Explosion starts with Grappling Web, which pulls players in and leaves them slowed around Alziriix. A large explosion then goes off around the boss if you do not get out in time.
What to do
Get out after the pull.
kite
Alziriix keeps dropping lightning AoEs on players and in extra random spots around the room.
What to do
Kite.
adds
Spider-Kith Horde-Menders channel heals. Spider-Kith Venifex are two-handed adds with a heavy attack. They both have around 500k HP.
What to do
Interrupt the heal and block the heavy.
Furthest-player cocoon and drag
An Ensnaring Spider will grab the furthest player, cocoon them, and start dragging them in. If the spider is not killed before the pull finishes, the cocooned player dies. It has around 1 million HP.
This did not trigger while solo, so the fight is soloable.
What to do
Make sure the furthest player is actually far away, then focus the spider while that player is being dragged in.
boss enrage
Alziriix periodically enrages. Throw a hoarvor sac at Alziriix to remove it.
What to do
Throw a hoarvor sac at Alziriix.
adds that drop sacs
Hoarvors roam the arena and drop sacs when killed. They have 7.8k HP.
What to do
Kill them so you can unenrage Alziriix.
adds
A swarm of broodlings spawns and chases players around the arena. They can be killed.
What to do
Cleave them down.
Defeating Gilded Alziriix will grant you the following buff:
Your Area Effects create diverging energy. Once every 15 seconds a location based Area Effect placed by you may begin to diverge, pulsing 1 path of energy every 0.8 seconds for 10 seconds dealing 5000 Magic Damage. Magical Multitudes only lasts 15 minutes and only takes effect within the bounds of the Night Market.
Footage from the dungeon is below.