Fields of Summer

Whenever a player casts a spell, that player may gain 2 life.
Whenever chaos ensues, you may gain 10 life.

Feeding Grounds

Red spells cost {1} less to cast.
Green spells cost {1} less to cast.
Whenever chaos ensues, put X +1/+1 counters on target creature, where X is that creature's mana value.

Quicksilver Sea

When you planeswalk to Quicksilver Sea and at the beginning of your upkeep, scry 4. (Look at the top four cards of your library, then put any number of them on the bottom and the rest on top in any order.)
Whenever chaos ensues, reveal the top card of your library. You may play it without paying its mana cost.

Velis Vel

Each creature gets +1/+1 for each other creature on the battlefield that shares at least one creature type with it. (For example, if two Elemental Shamans and an Elemental Spirit are on the battlefield, each gets +2/+2.)
Whenever chaos ensues, target creature gains all creature types until end of turn.

Murasa

Whenever a nontoken creature enters, its controller may search their library for a basic land card, put it onto the battlefield tapped, then shuffle.
Whenever chaos ensues, target land becomes a 4/4 creature that's still a land.

Selesnya Loft Gardens

If an effect would create one or more tokens, it creates twice that many of those tokens instead.
If an effect would put one or more counters on a permanent, it puts twice that many of those counters on that permanent instead.
Whenever chaos ensues, until end of turn, whenever you tap a land for mana, add one mana of any type that land produced.

Naya

You may play any number of lands on each of your turns.
Whenever chaos ensues, target red, green, or white creature you control gets +1/+1 until end of turn for each land you control.

Izzet Steam Maze

Whenever a player casts an instant or sorcery spell, that player copies it. The player may choose new targets for the copy.
Whenever chaos ensues, instant and sorcery spells you cast this turn cost {3} less to cast.

Takenuma

Whenever a creature leaves the battlefield, its controller draws a card.
Whenever chaos ensues, return target creature you control to its owner's hand.

Academy at Tolaria West

At the beginning of your end step, if you have no cards in hand, draw seven cards.
Whenever chaos ensues, discard your hand.

Stairs to Infinity

Players have no maximum hand size.
Whenever you roll the planar die, draw a card.
Whenever chaos ensues, reveal the top card of your planar deck. You may put it on the bottom of your planar deck.

Grand Ossuary

Whenever a creature dies, its controller distributes a number of +1/+1 counters equal to its power among any number of target creatures they control.
Whenever chaos ensues, each player exiles all creatures they control and creates X 1/1 green Saproling creature tokens, where X is the total power of the creatures they exiled this way. Then planeswalk.

Isle of Vesuva

Whenever a nontoken creature enters, its controller creates a token that's a copy of that creature.
Whenever chaos ensues, destroy target creature and all other creatures with the same name as that creature.

Goldmeadow

Whenever a land enters, that land's controller creates three 0/1 white Goat creature tokens.
Whenever chaos ensues, create a 0/1 white Goat creature token.

Morphic Tide

When you encounter Morphic Tide, each player shuffles all permanents they own into their library, then reveals that many cards from the top of their library. Each player puts all artifact, creature, land, and planeswalker cards revealed this way onto the battlefield, then does the same for enchantment cards, then puts all cards revealed this way that weren't put onto the battlefield on the bottom of their library in any order. (Then planeswalk away from this phenomenon.)

Otaria

Instant and sorcery cards in graveyards have flashback. The flashback cost is equal to the card's mana cost. (Its owner may cast the card from their graveyard for its mana cost. Then they exile it.)
Whenever chaos ensues, take an extra turn after this one.