Pioneer Masters

Boros Reckoner | Creature | Minotaur Wizard | Whenever Boros Reckoner is dealt damage, it deals that much damage to any target. {R/W}: Boros Reckoner gains first strike until end of turn. | Howard Lyon

Aurelia's Fury | Instant | | Aurelia's Fury deals X damage divided as you choose among any number of targets. Tap each creature dealt damage this way. Players dealt damage this way can't cast noncreature spells this turn. | Tyler Jacobson

Counterflux | Instant | | This spell can't be countered. Counter target spell you don't control. Overload {1}{U}{U}{R} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.") | Adrián Rodríguez Pérez

Sire of Insanity | Creature | Demon | At the beginning of each end step, each player discards their hand. | Joshua Raphael

Rakdos's Return | Sorcery | | Rakdos's Return deals X damage to target opponent or planeswalker. That player or that planeswalker's controller discards X cards. | Daarken

Ruric Thar, the Unbowed | Legendary Creature | Ogre Warrior | Vigilance, reach Ruric Thar, the Unbowed attacks each combat if able. Whenever a player casts a noncreature spell, Ruric Thar deals 6 damage to that player. | Tyler Jacobson

Chromanticore | Enchantment Creature | Manticore | Bestow {2}{W}{U}{B}{R}{G} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.) Flying, first strike, vigilance, trample, lifelink Enchanted creature gets +4/+4 and has flying, first strike, vigilance, trample, and lifelink. | Min Yum