Firstly, the "scattered crystals", dropped by Crystal Hydras, are not being accepted by the Effusion summoning collector in the frozen mummy room. The box just rejects the item. I have seen it accept the shattered, broken, fractured, and fragmented crystals from other creatures in the area.
Related to that problem, you need 6 items to summon effusion, but only 5 appear to drop on any monsters right now. "Fractured" from Crystal Daemons, "Shattered" from Crystal Sea Serpents, "Scattered" from Crystal Hydras, "Crystal Fragments" from Crystal Vortex, and "Broken" from Frozen Mummies appear to be dropped normally, but this should still leave "Jagged" crystals necessary. Crystal Guardians, I believe, are supposed to drop these, but having killed quite a few, they're only dropping the same "fractured" crystals as the daemons. These two problems make it impossible to fight Shimmering Effusion to complete this part of the peerless quest.
Related to the Prism of Light, though it may not be the bug, can I confirm whether the crystal sea serpents are still dropping Icy Hearts for the Prism of Light Collector? I have killed nearing 50 or more of them and seen no sign of any sort of special item from them. I know it's been said the ML guide webpage is a bit out of date still, so I'm not sure if this monster is still dropping what that page says it should.
Slightly less related to that, I have a couple versions of the final gem collector, neither of which are accepting the Gem of Bedlam, and the one I just picked up from the Collector Maker won't accept my Gem of Blight either. I'm not sure which item has which flaw, but there might still be a problem with the collector at this time.
I hope all that's enough information to work from.

Edit, November 29: Ran through the Prism again for kicks, found the Guardians were dropping a different crystal than before, this time the scattered crystals from the hydras, rather than the fragments from the daemons. Go figure. Also, during the house drop I found several "crushed" crystals lying about in some houses, so those were probably what the guardians were originally dropping, rather than the "jagged" ones I mentioned above. That info might help in working out what all needs touching up. I hope.
