Burning-Tree Emissary

When Burning-Tree Emissary enters the battlefield, add {R}{G} to your mana pool.

Scavenging Ooze

{G}: Exile target card from a graveyard. If it was a creature card, put a +1/+1 counter on Scavenging Ooze and you gain 1 life.

Elvish Mystic

{T}: Add {G} to your mana pool.

Nykthos, Shrine to Nyx

{T}: Add {1} to your mana pool. {2}, {T}: Choose a color. Add to your mana pool an amount of mana of that color equal to your devotion to that color. (Your devotion to a color is the number of mana symbols of that color in the mana costs of permanents you control.)

Llanowar Elves

Tap to add green mana to your mana pool. This tap can be played as an interrupt.

Walking Ballista

Jadelight Ranger

When Jadelight Ranger enters the battlefield, it explores, then it explores again. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard. Then repeat this process.)

Nissa, Who Shakes the World

Whenever you tap a Forest for mana, add an additional {G}. +1: Put three +1/+1 counters on up to one target noncreature land you control. Untap it. It becomes a 0/0 Elemental creature with vigilance and haste that's still a land. −8: You get an emblem with "Lands you control have indestructible." Search your library for any number of Forest cards, put them onto the battlefield tapped, then shuffle your library.

Veil of Summer

Draw a card if an opponent has cast a blue or black spell this turn. Spells you control can't be countered this turn. You and permanents you control gain hexproof from blue and from black until end of turn. (You and they can't be the targets of blue or black spells or abilities your opponents control.)

Vivien, Arkbow Ranger

+1: Distribute two +1/+1 counters among up to two target creatures. They gain trample until end of turn. −3: Target creature you control deals damage equal to its power to target creature or planeswalker. −5: You may choose a creature card you own from outside the game, reveal it, and put it into your hand.

Voracious Hydra

Trample Voracious Hydra enters the battlefield with X +1/+1 counters on it. When Voracious Hydra enters the battlefield, choose one — • Double the number of +1/+1 counters on Voracious Hydra. • Voracious Hydra fights target creature you don't control.

Once Upon a Time

If this spell is the first spell you've cast this game, you may cast it without paying its mana cost. Look at the top five cards of your library. You may reveal a creature or land card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

Castle Garenbrig

Castle Garenbrig enters the battlefield tapped unless you control a Forest. {T}: Add {G}. {2}{G}{G}, {T}: Add six {G}. Spend this mana only to cast creature spells or activate abilities of creatures.