That quest requires a full alliance (18 people) to complete. It has 3 versions of it... Windurst (Maze of Shakrami), Bastok (Gusgen Mines), San d'Oria (Ordelle's Cave).
There will be a good deal of dying in that quest. I don't know the one for Windurst, but the one for Bastok is hard as hell. Thanks to the Bogys that spawn near the NM slime.
It is usually a good idea to get some level 35+ to clear the way to where the NM spawns. Due to the level cap, you cannot have anyone to heal the alliance from outside. But people outside can kill the mobs that spawn nears the NM.
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Amanada (Cerberus-Retired) (aka MaiNoKen/Steven)
-- Thank you for the fun times in Vana'diel
Art for the sake of art itself is an idle sentence.
Art for the sake of truth, for the sake of what is
beautiful and good — that is the creed I seek.
- George Sand
A designer knows he has achieved perfection,
not when there is nothing left to add,
but when there is nothing left to take away.
- Antoine de Saint-Exupéry