Guilds of Ravnica

Firemind's Research | Enchantment | | Whenever you cast an instant or sorcery spell, put a charge counter on Firemind's Research. {1}{U}, Remove two charge counters from Firemind's Research: Draw a card. {1}{R}, Remove five charge counters from Firemind's Research: It deals 5 damage to any target. | Grzegorz Rutkowski

Ionize | Instant | | Counter target spell. Ionize deals 2 damage to that spell's controller. | Chase Stone

Niv-Mizzet, Parun | Legendary Creature | Dragon Wizard | This spell can't be countered. Flying Whenever you draw a card, Niv-Mizzet, Parun deals 1 damage to any target. Whenever a player casts an instant or sorcery spell, you draw a card. | Svetlin Velinov

Expansion | Instant | | Copy target instant or sorcery spell with mana value 4 or less. You may choose new targets for the copy. | Deruchenko Alexander

Chamber Sentry | Artifact Creature | Construct | Chamber Sentry enters the battlefield with a +1/+1 counter on it for each color of mana spent to cast it. {X}, {T}, Remove X +1/+1 counters from Chamber Sentry: It deals X damage to any target. {W}{U}{B}{R}{G}: Return Chamber Sentry from your graveyard to your hand. | Adam Paquette

Steam Vents | Land | Island Mountain | ({T}: Add {U} or {R}.) As Steam Vents enters the battlefield, you may pay 2 life. If you don't, it enters the battlefield tapped. | Jonas De Ro