Careful Study was good enough to be played in decks where you could abuse the discard, Faithless Looting is good enough that you can play it in most red decks regardless
Nothing extravagant, but we do have a handful of cards that were in the $10ish range before the deck was revealed, like Whip of ErebosWhip of Erebos, Titania, Natures ForceTitania, Natures Force, Professor OnyxProfessor Onyx, and Dryad ArborDryad Arbor
Treat phased-out permanents and anything attached to them as though they don't exist until their controller's next turn.) Instant Sivitri, Dragon Master +1: Until your next turn, creatures can't attack you or planeswalkers you control unless their controller pays 2 life for each of those creatures
The Mouth of Sauron The Mouth of Sauron can potentially amass you a large army, and blue has some good flicker effects that would allow you to reuse this ETB trigger
Being a mana rock is a plus
14 Zul Ashur, Lich Lord They Won't Stay Dead