Basically any and every card that synergizes well with Bolas planeswalker and creature cards are in Grixis colors, so go wild and build an all-out Nicol Bolas deck
Images courtesy of The Pokmon Company On Friday, March 21st, Pokmon TCG Pocket teased their next mini-set, Shining Revelry
Its easy to see why, as Commander decks are more or less synonymous with taking a few turns to get going via ramping mana, setting up mana rocks, playing supports cards and so on
For the rest I'd recommend more tutors to find Jeskai Ascendancy like Enlightened Tutor and Idyllic Tutor, some good recursion like Underworld Breach, and better mana-fixing like shocks / ABU / fetches
As of M15, the letters for the rarity are printed on the card, C, U, R, M, next to the collector number and rare and mythic have a holofoil oval with the planeswalker symbol