In a lot of situations, putting something on the bottom of the library is much harder to overcome than putting it in the graveyard
1Ascendant Packleader
Playing Xorn on curve is a mistake unless you are creating treasure tokens by attacking with a creature like Hoard Robber, or are casting an Instant that turn which produces a Treasure token
You pay one blue mana, then any amount of additional mana, and allow everyone else at the table to chip in
From hard stax pieces like Elesh Norn, Mother of Machines, Drannith Magistrate, and Archon of Emeria to softer disruption in Thalia, Guardian of Thraben or Ranger-Captain of Eos, white disrupts and stops your opponents better than any color except maybe blue and its countermagic
If you choose two creatures as targets with this spell and only one target is legal as the spell resolves, no fight will occur and no damage will be dealt, but you will still proliferate