Filtered: Loki & Sif
But you and Val are also limited resources, and so is Thor. Simple strategy tells me we should spend your strength on what we need most, which, honestly, is not a gaol.
An underground dungeon would certainly serve for any of our own people. And if something more powerful were to attack us, it would likely have done additional damage to Midgard, so we might simply refer it to them. But this is a pojnt for the council and Thor, I think, and we can discuss it then.
It's unfortunate that you have enough experience to compare prisons.