[@Double Capybara] You made puns! I approve.

The worldbuilding of Raka and Arpeggio as some kind of dream fission reactor is really solid, and I hope we'll keep seeing Ilunabar's musical themes in stuff like this. Is there any spiritual life native to Raka and feeding on/tampering with dreams, or not yet?

As for the domain switch/addition, I think it's entirely viable. You may want to keep building on the themes of desire, pleasure or escapism in there, since I feel like that's what you're going for with Ilunabar rather than undirected whim. Anyway, the only name suggestions I can think of are 'Fancy' and 'Reverie', which are both pretty much just positively-connotated synonyms of Fantasy, which is probably the best fit on a purely definitive level.