Istredd thinks Solvunn might very well end up coasting in the background. Waiting for everyone else to kill each other. It's not the worst strategy. For all they know, Nocwich plans to do the same, and the Feywilds, which they know nothing about still.

Castiel was not the only person who released it. The shrine creature was very clever, it was talking to all of us in voices that could persuade us. He has no idea what voice Castiel heard. Perhaps it was God. Either way, Istredd wouldn't call that his mistake. It was a group effort and decision in the end ... while out of their minds.

If only we could trust Hayle. Istredd was there a short time and he already wants to go back. It is unsurprisingly his ideal sort of place, albeit just another type of gilded cage. A crystal cage, with so so so many books. If he didn't have better reason to sleep in bed with Lucifer, he might have snuck off to the library to read what he could before they were forced to leave.

He picked his partner over books, a true sign of love.

It seems like it could withstand pressure.