Our information about the Nirduks during the 580s is fragmentary at best. Sonek died, Kareelmola posed as the deceased Kalek, and Streck moved the clan to its mountain base. Streck's run-in with a prismatic spray and possible trip to another plane probably happened shortly before this period (since it would have been hard to encounter a prismatic spray during it and Streck's personal calendar is known to be fifty years off by AK 590). The clan lost its ink and spellbooks but were able to draw on a stockpile of old-style burnable magic items (possibly obtained during their Organization days) that lasted until ink and old-style magic were rediscovered.
By AK 590, the alliance between the Nirduks and the shades was no longer secret. In the early months of that year, they got along very well indeed: both parties wanted Ganeth Barshen dead (the Shade Lord because he'd been quested by the Wind Temple to stop her from becoming a god, Streck because he was a Barshen -- and a Barshen flaunting a Nirduk cloak at that) and they mounted several joint assassination attempts. This eventually got to be too expensive (in both items and operatives -- the same problem the Organization seemed to have with Ramola's vendetta against the party way back when), so Streck and Ganeth signed a mutual non-aggression pact on AK 590/5/23. This put a slight damper on the shade/Nirduk alliance; at one point Streck pulled his people off air support for a planned shade/kobold ambush of a halfling community the party was guarding. And after the party had foiled an operation on Mt. Kathul (I've forgotten exacty what it was), they found a young high elf named Ekali sitting on the front steps; she just came by to tell "Uncle Ganeth" that she'd heard from "Uncle Streck" that he was coming to live with them, was very excited, and wanted to know when he was going to move in...