Serini's Gate, also known as Kraagor's Tomb and Kraagor's Gate, is the fifth of the gates sealing the rifts of the Snarl. Located near the North Pole, it is built over the area where the dwarven Barbarian Kraagor was killed trying to hold off the Snarl while his companions, Dorukan and Lirian, were sealing it. Built by Serini Toormuck in his honor, it contains some of the strongest monsters in the world, reflecting his belief in the power of physical might.
It's hidden in massive complex which consists of dozens, if not hundreds of separate "tombs" filled with extremely powerful monsters. The complex itself is built with multidimensional stone, which apparently prevents anyone from passing through the wall so the only way to reach the gate is to fight through the small army of monsters and clear the tombs one by one.
Team Evil arrived at the Gate well in advance of the Order of the Stick, and have been systematically clearing each tomb to search for the Gate with the help of Oona and the local population of Bugbears. However, the Monster in the Darkness is secretly working to foil their attempts, by painting exes on doors to tombs that they have not in fact cleared yet.
O-Chul and Lien arrived at the gate sometime after Team Evil, sent by Lord Hinjo on a reconnaissance mission. After an inconclusive skirmish with Oona and Lancer, they have been holed up in the mountains overlooking the entrance to the tombs observing Team Evil and are aware of MitD's activities.