Well, I have learnt two things from this. First is that Alide is very beatable if everyone is fighting, and probably trivially so if we can do something about that initial barrage of darts. Second we have a fair bit of leeway before a critical failure although I would rather not use any of it. Also, I don't suppose Alide is obligated to kill in alphabetical order? Because that would be rather convinient if true.
I don't really know what boon to ask for, but I think it would be overly cruel to leave anyone behind at this stage. Perhaps try for a better cure? That seems like a useful spell right now.
And for next steps (after healing and curing everyone), unless we are getting a free pass to the exit door, head back to the previous room (to deal with the anti-magic) then back in and use Open to bypass the room. Or we try for a fair fight in the starting room via waiting, it seems like Alide still needs to turn up at random like a normal floor boss.
Oh, and any ideas for dealing with darts? Looks like open does indeed bypass the existing magical defences but perhaps we can find something that qualifies as "force". Maybe experement by throwing rocks at Beck, I'm sure she will love that.