Guilds of Ravnica

Boros Challenger | Creature | Human Soldier | Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.) {2}{R}{W}: Boros Challenger gets +1/+1 until end of turn. | Gabor Szikszai

Justice Strike | Instant | | Target creature deals damage to itself equal to its power. | Clint Cearley

Legion Guildmage | Creature | Human Wizard | {5}{R}, {T}: Legion Guildmage deals 3 damage to each opponent. {2}{W}, {T}: Tap another target creature. | Zack Stella

Swathcutter Giant | Creature | Giant Soldier | Vigilance Whenever Swathcutter Giant attacks, it deals 1 damage to each creature defending player controls. | Aaron Miller

Truefire Captain | Creature | Human Knight | Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.) Whenever Truefire Captain is dealt damage, it deals that much damage to target player. | Chris Rallis

Integrity | Instant | | Target creature gets +2/+2 until end of turn. | Ben Maier

Conclave Cavalier | Creature | Centaur Knight | Vigilance When Conclave Cavalier dies, create two 2/2 green and white Elf Knight creature tokens with vigilance. | Tomasz Jedruszek

Conclave Guildmage | Creature | Elf Cleric | {G}, {T}: Creatures you control gain trample until end of turn. {5}{W}, {T}: Create a 2/2 green and white Elf Knight creature token with vigilance. | Jason Rainville

Join Shields | Instant | | Untap all creatures you control. They gain hexproof and indestructible until end of turn. (They can't be the targets of spells or abilities your opponents control. Damage and effects that say "destroy" don't destroy them.) | Winona Nelson

Ledev Champion | Creature | Elf Knight | Whenever Ledev Champion attacks, you may tap any number of untapped creatures you control. Ledev Champion gets +1/+1 until end of turn for each creature tapped this way. {3}{G}{W}: Create a 1/1 white Soldier creature token with lifelink. | Daarken

Worldsoul Colossus | Creature | Elemental | Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.) Worldsoul Colossus enters the battlefield with X +1/+1 counters on it. | James Paick

Flower // Flourish | Sorcery // Sorcery | | Search your library for a basic Forest or Plains card, reveal it, put it into your hand, then shuffle. // Creatures you control get +2/+2 until end of turn. | Dmitry Burmak