Oh, no doubt Alfred can jail any of them, I said as much already. But do you think the Blackstaff has never had to track someone in fog? HARRY has done that with Arianna. I don't think that alone is enough. His worst outcome is Harry gets killed. his best outcome is likely that Alfred does manage to get them all before they get off the island. By running to the dock or flying off.

That was against two who, in open combat, he beats easily even in Chicago. Lara lost it. Whamps are not someone who can attack a wizard at a distance and close to hand to hand. Being on Demonreach meant he could do it casually, and subdue them without hurting them.  And two, not 7 or 8, all more powerful than those two. If he attacks the Wardens, LtW and Eb open up, and who knows what Mai may be able to do? And the sinking in the ground - why do we assume LtW is the only shapeshifter? And it would only take one Warden to escape, then when you are against LtW and Eb, both better than you - they get you. Maybe he could face off against them - though the Blackstaff, I don't know. But far from proven.

And yet, Ancient Mai didn't seem to be aware of what Demonreach really is, for one example.

(I suppose her scenes on the island might be read as having been dissembling to not speak about it in front of Harry and the other Wardens who aren't cleared to know ... but Harry suddenly acting weirdly confident on that particular ground should have been an excellent reason for someone who understands what the island is and had tried to sentence him to death before to absolutely not step on its ground.)