Oh. I should also mention that Be'lakor the Dark Master has his own spell lore and unique rules. A lot of them are Ulgu themed, although that might be a coincidence because of Be'lakor's obsession with "Shadow" and "Night". "Whispers in the Darkness", "Night Wards", "Shadow Shroud", "Master of the Shadows". All of these skills have Ulgu-ish names and aside from Night Wards, Ulgu like effects. Aside from Coils of the Serpent and Bolt of Dark Light, his remaining spells also have an Ulgu theme. Nightmare (self explanatory), Fog of Death (self explanatory), and maybe Curse of the Dark Master?
I should also mention that the Lore of Shadow might be one of the most common spell lores btw. I haven't done the counting just yet, but the Colleges of Magic, Beastmen Bray Shamans, Dark Elf Sorceresses (Morathi in particular), High Elf Mages, Wood Elf Spellsingers/weavers, Shadow Dancers, Shadow Warriors (Probably), Mist Mages (Most Likely), Mist Walkers (Probably), Drycha (Standard Branchwraith casts from Life, she casts from Shadow), Slann, the Fey Enchantress, the Blue Scribes, Kairos Fateweaver, Lucrezzia Belladonna (Apocryphal, but she chooses Shadow or Death), Vampires, Slaanesh Mages/Daemons are naturally attuned to Ulgu, Chaos Sorcerors in general, Dark Emissaries, Sayl the Faithless, the Lammasu (look them up, you might be surprised), and Fimir Balefiends.
I feel like I missed something. In Boney's universe there's also the Kurgan Shaman of the Eight, which might be a separate tradition from traditional Chaos Sorcerors (like the Vitki of the Norse, which are not necessarily Chaos Sorcerors btw, they're Hedge Wizards in the mechanics for WFRP not Chaos Sorcerors). And there's the Fire Spire of Praag but that place was destroyed. Oh, and there's the Gnomes, who are naturally attuned to Ulgu. Whether they exist or not is up to Boney, but they live in the Mirror/Midden Moors in Middenland.