Kinda on the topic, I'd like to throw an idea for an elite dungeon of ascension members. Following in the standard of ed1-3 have the 3 boss battle but like RoTS have the 6 legio boss rotate in the first two battles with the third being against their Guthix creation, after seeing the breakaway factions failure of Gielinor.
Perhaps with how the EGWD will go they may change from their belief of Guthix and see the ways of another god.
With the order descending futher into madness they would likely have taken even more creatures nearby and processed them into crystaline creatures.
Since they were powerful mages I'm sure it would also be fitting to create codex fitting of their order, learning some of their secrets like throwing electrical AoE and creating lines of ascension to a target.
Also creating skilling oppertunities. Theres nothing like grinding something down and throwing it in a potion to find out what it does! From their research of runestones and Guthix's tears they may have devoloped a form of runecrafting to enhance their magic and capturing vibrant wisps from the nearby area leading to invention discovery.
Just throwing this idea out here as its no good sat in my head lol