During each player's turn, that player may play a land or cast a spell from among cards exiled with this enchantment, and they may spend mana as though it were mana of any color to cast that spell
Adelbert Steiner Adeline, Resplendent Cathar Adeline, Resplendent Cathar Adriana, Captain of the Guard Adun Oakenshield Arna Kennerd, Skycaptain Arthur, Marigold Knight Arvad the Cursed Aryel, Knight of Windgrace Balan, Wandering Knight Bartolom del Presidio Basri, Tomorrow's Champion Caradora, Heart of Alacria Cecil, Dark Knight Cecil, Redeemed Paladin Celes, Rune Knight Danitha Capashen, Paragon Danitha Capashen, Paragon Danitha, Benalia's Hope Danitha, New Benalia's Light Dion, Bahamut's Dominant Edgar Markov Elder Arthur Maxson Elder Owyn Lyons Elenda and Azor Elenda, Saint of Dusk Elenda, the Dusk Rose Ellivere of the Wild Court Freya Crescent Galea, Kindler of Hope Garland, Knight of Cornelia Garland, Royal Kidnapper Haakon, Stromgald Scourge Haytham Kenway Ihsan's Shade Imodane, the Pyrohammer Inti, Seneschal of the Sun Jerrard of the Closed Fist Josu Vess, Lich Knight Judge Magister Gabranth Kain, Traitorous Dragoon Kwende, Pride of Femeref Lena, Selfless Champion Livio, Oathsworn Sentinel Mazzy, Truesword Paladin Merry, Esquire of Rohan Mrton Stromgald Nadaar, Selfless Paladin Nymris, Oona's Trickster Olivia, Mobilized for War Paladin Danse, Steel Maverick Paladin Elizabeth Taggerdy Rafiq of the Many Rem Karolus, Stalwart Slayer Ria Ivor, Bane of Bladehold Sarevok, Deathbringer Seifer Almasy Sentinel Sarah Lyons Shanid, Sleepers' Scourge Shay Cormac Sidar Jabari Sidar Jabari of Zhalfir Sidar Kondo of Jamuraa Sir Shandlar of Eberyn Squall, SeeD Mercenary Sylvia Brightspear Syr Alin, the Lion's Claw Syr Armont, the Redeemer Syr Cadian, Knight Owl Syr Carah, the Bold Syr Elenora, the Discerning Syr Faren, the Hengehammer
Originally, Vampires in Magic were concepted as mono-Black, with early luminaries like Sengir Vampire, Baron Sengir, and Crovax the Cursed
If a spell has multiple types, and one of those types is creature (such as an artifact creature), casting it won't cause prowess to trigger
Adding 2 mana in a combination of colors enables lots of multicolor cards like Omnath, Locus of All, and Niv-Mizzet Reborn which would be far harder to use otherwise
Using an enchantment like Animate Dead on it in your graveyard allows you to create an infinite loop
