Oooh, interesting.

­Blightning, Bog Down and Augur of Skulls suggests turn3 is acceptable for this effect, in a way Hymm to Tourach isn't any more.

This makes it into "Target player empties their hand over two turns" - which is scary powerful - but it'll be all you cast T3 and T4 if you use it for that. And Skull Fracture suggests this is a very aggressive flashback cost for it.

Where it really shines is that it means you don't need to dedicate anywhere near as much of your deck to forced discard, so you can leave a lot more room to do other stuff.

so, powerful enough to be exciting - yet costly enough to maybe be fair? And hard to splash. You might even persuade me to play black, to run this.

I think that you are right that the flashback cost needs to be just a tad higher. Fixing.....Done

still too cheap.

t1. 1st tourach
t2. 2nd tourach
t3. flashback
t4. flash again

over 4 consecutive turns you guarantee opponent has empty hand by turn 6.

flashback cost at least 7 or 8

Sure if you're running Dark Rituals and casting nothing else.