Been ages since I posted any tips, so here's my secret Prism tricks -
You don't need a tamer. Best if you have a second account, if not, just buy 2 horses (or any other 2 pets).
1) Leave 1 at the crystal lattice room 1 or 2 tiles away from east most part of the wall. "All stay" this horse. If it's right against the wall, there's a spot that the daemons can cast through and it will kill the horse. If you have a second account, just leave a character there.
2) Go into the daemon room and kill each of the daemons once so that you have the maximum amount of time before they un-spawn/respawn. Don't want any rude surprises.
3) Lure all of them (there are 6 if I remember correctly) to the east most wall. Invis/hide and wait until they target your horse in the lattice room.
4) Once you have the daemons occupied, move to the south east corner of the room. Ride the 2nd horse to this spot and "All stay". Or use the context menu to get this horse to follow you to this spot.
5) Move up and down along the east wall to lure the serpents and hydras into following you to the part of the room where they can aggro your 2nd horse. You might also want to kill each once before starting to reset the un-spawning timer.
6) There are safe spots away from the shore while still being near enough to the water for fishing.
Other Prism related tricks:
1) A Hydra will roar like a dragon before firing its breath weapon. Once you hear that roar, hide immediately or use a smoke bomb. If you are hidden, the multiple fireballs will not target you.
2) Besides holding one of the keys for getting to the peerless, Crystal Sea Serpents have a couple of goodies - horned hide, serpent scales, icy heart and a dagger called "someone's dagger".
3) Firstly, that dagger? It's BLESSED. I love blessed items. So almost all my chars carry one.
4) Serpent and dragon scales are worth 20 points each to the Brit Library donation
5) Setup a macro to use the Prism ticket. This acts as an instant escape button should you need to flee.