Am I projecting things or is the Phyrexian symbol blatant in the saga art when you take out the upper and lower arcs? Ditto for Ringhart Crest, the spear in Alrund's Epiphany, and the sundogs in various cards' backgrounds.
I believe that if you're not casting the spell from your hand then Knowledge Pool's restrictions won't interfere. Bash to Bits and Ancient Grudge can be flashed back to destroy the Pool, or you could cast Welcome to the Fold from exile via Madness to steal Lavinia and give the player a taste of their own medicine. If you don't have a discard enabler already in play when the Pool comes down then you'd have to wait and fill your hand, then discard one of these at end of turn to get them where they need to be.
Eternal Scourge and Misthollow Griffin can both be cast from exile so you can still cast them after they wind up in the Pool.
Assuming this is a Commander deck then casting your commander from the Command Zone should bypass the lock. Maybe add black, run Sedris as your commander, and Unearth whatever you can manage to get into your graveyard? Memnarch is the only mono-blue commander I can think of offhand that would have a meaningful direct effect (stealing Lavinia), but Venser would let you reset things for a turn. Joven as the commander would be a liability in most any other matchup but it may get the point across If you're willing to go green then Freyalise can keep coming back to kill the Knowledge Pool over and over again.
If you can get a Titania's Song in play beforehand then the Knowledge Pool will be negated.
Eternal Scourge and Misthollow Griffin can both be cast from exile so you can still cast them after they wind up in the Pool.
Assuming this is a Commander deck then casting your commander from the Command Zone should bypass the lock. Maybe add black, run Sedris as your commander, and Unearth whatever you can manage to get into your graveyard? Memnarch is the only mono-blue commander I can think of offhand that would have a meaningful direct effect (stealing Lavinia), but Venser would let you reset things for a turn. Joven as the commander would be a liability in most any other matchup but it may get the point across
If you can get a Titania's Song in play beforehand then the Knowledge Pool will be negated.