When considering upgrades for this deck, Grand Arbiter Augustine IV is worth a look-in owing to how it reduces the cost of your blue and white spells, and (rather cruelly) taxes your opponents for every spell they cast
In point of fact, there are a couple singles that are commanding an excruciatingly high price tag worthy of discussion, too
Deathrite Shaman is so good, so powerful , that it has been banned in both Modern and Legacy
I appreciate that its a mana dork itself instead of just enabling other cards to produce mana, and your opponents have to kill this glimmer twice
So much so, in fact, that most players dont even seem to mind it being a Universes Beyond set anymore
But for an additional two mana with Entwine, you can do both