Kesizma is an anagusi domain in a separate time branch.
The name was one of the very few words that the party managed to understand from Maal when they met her during Session 4. At the end of the session, they saw Maal entering a stable portal and on the other side they glimpsed a gigantic cave whose entire interior had been made into a city.
Kesizma was further seen during Session 8 when they launched an invasion in the rigasian Zones; they demonstrated having smoother control of portals than Rigasia, and brought quite a big number of intelligent beasts that formed the spearpoint of their attack.
During the second arc, Kesizma came to the front of the story as part of the Rigasia/Kesizma War and the party learned many other things about them: they hold domain over several timelines, not necessarily synced in time with the rigasian one, and their cities are not in regular timelines but in “caves” that they made “by folding firmament into itself to make a whole”.