In paper, they all cost between $120 and $320, but on MTGO , each was less than $5
Piru, the Volatile With Piru, the Volatile around, you can opt to pay the mana and keep a 7/7 flying and lifelink dragon around, or let it die to deal 7 damage to each nonlegendary creature
Prevent all combat damage that would be dealt this turn by non-Spider creatures
Regardless of that it is fair to say that tapping your lands to draw cards is more of a tempo cost, particularly in blue, than leaving them open
Its your sac outlet, card draw engine, and spot removal all in one tidy package
Herald of Anguish can also turn those extra Bone Saws into removal spells