Serras Sanctum
Can Be Found In: Dark Beginning 1 (DB1-EN163), Metal Raiders (MRD-EN036), Structure Deck: Spellcaster's Judgment (SD6-EN005), Starter Deck 2006 (YSD-EN012), Champion Pack: Game Two (CP02-EN003), Battle Pack 2: War of the Giants (BP02-EN005), Starter Deck: Joey (SDJ-017), Dark Legends (DLG1-EN034), Retro Pack (RP01-EN033) Spell cards are usually the ones with the better outcomes
For regular upgrades I highly recommend: Vito, Thorn of the Dusk Rose, Mondrak, Glory Dominus, Anointed Procession, Parallel Lives, Eerie Ultimatum, and you can also run the Cat Oven combo with Cauldron Familiar + Witch's Oven + Clock of Omens, and there's the Ballista Combo Heliod, Sun-Crowned + Walking Ballista, and finally the Exquisite Blood Combo since the deck already runs the other piece Sanguine Bond One Down, Three to Go
D&D campaigns are (very often) all about powerful characters that take on evil doers to save the world, or at the very least a town or city, from destruction