silence could probably be fixed by limiting the ability to only work the turn the spell was played and then get back its original ability (which does nothing on its own). Sosac may not be an issue since it costs 80 health to chain like that (at least with my fix added). First thing I thought of was using this with rewind, which probably isnt much better than eternity. Quintessence is also decent with this card, especially with SoW added (how about some reflect cheese to that; you can finally make more than 6 non-psions hit their owner). Using Precognition in 30+card decks finally makes sense (well it did actually make sense in Blarp, too and knowing your opponents hand is nice, but this makes it better). I like it and dont think its op, provided you use that fix.
You can also double SoR Nymphs, flying eternities, Pharaohs and creatures with mitosis.
Edit: alternatively you could limit it to spells that require targetting. That would remove most of the obviously op mechanics, while allowing more player interaction, since your opponnent may want to overwrite the ability.
