Demonrats invade our privacy?! Say it isn’t so! … Too funny! 
Ah the Uridezu are a fictional species from Dungeons and Dragons, which makes them in my book, workable as egregoric beings from the collective human astral. Every writer, Dungeonmaster and D&D player that has made stories with these in them have contributed to their development as thoughtforms.
I would not expect them to have significant ability to affect results in the physical: you would have to supply all the power for them to work with. They would be interesting for writers and psychonauts to investigate, imo.
They won’t have any sigils, those are from old grimoires and as these are not from the occult community but the gaming community, it’s unlikely anyone named a name and made a sigil. You are the first person to use this species name on BALG that’s for sure. It may be that outside of possibly individual D&D games none are named (I can imagine “the King of the Uridezu” popping up in some DMs imagination).
Benefits? they’re a mob enemy aren’t they, so probably something baneful. Make it up: you’re in chaos magick land so you can do what you like. You don’t have much weight from the collecive unconscious boxing this thoughtform in.
For ideas on where you can take it, look up here how one member worked with the Daedric Princes from Elder Scrolls. As lenses for your own ability, it works just fine.
Check out servitor creation, which is closely related: he only difference being it’s someone else’s thoughtform you are … borrowing, sort of… 
But you can use this to develop the form into something useful.