msem-instigator

Create a number of 3/3 green Elemental creature tokens equal to the number of differently named lands you control.
Fuse (You may cast one or both halves of this card from your hand.)

Whenever Rolling Homestead becomes a creature, nourish 1. (To nourish 1, either put a +1/+1 counter on this creature or create a 1/1 white Citizen creature token.)
Crew 2 (Tap any number of creatures you control with total power 2 or greater: This Vehicle becomes an artifact creature until end of turn.)

(Add a quest counter as this enters. Sacrifice after 3.)
Whenever a creature you control attacks alone, add a quest counter.
Target creature can't block this turn.
Gain control of target creature until end of turn. Tap it. It becomes attacking.
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Gain control of target creature until end of turn. Untap that creature. It gains haste until end of turn. Create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

Artifacts and lands enter tapped.

For each nontoken enchantment you control, conjure a duplicate of it into your hand. Until the end of your next turn, you have no maximum hand size.
Exile Root Duplication.

(Activate each submodule once as a sorcery. When this enters, activate one submodule for free.)
{G}{G}{G}: Seed
Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.
{G}{G}{G}: Soil
Destroy target noncreature permanent.
{G}{G}{G}: Stem
Root Module gains “You may play an additional land on each of your turns.” and “Lands you control are every basic land type in addition to their other types.”

When Rootbound Awakener enters, create a green Aura enchantment token named Vivification attached to target creature or land. The token has enchant creature or land and “Enchanted permanent is a creature with base power and toughness 5/5 in addition to its other types.”

Defender
As long as you control an enchantment, Rooted Cavalier has vigilance and can attack as though it didn't have defender.

{T}, Sacrifice Rootshambler: Untap all basic lands you control.

{1}{G}, {T}, Discard a card: Another target creature you control gets +X/+X until end of turn, where X is 4 minus that creature's power.

Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)

When Roseblood Hart enters, choose one —
• Destroy target artifact.
• Create a Treasure token.

Instant, sorcery, and enchantment spells you cast cost {1} less to cast.

Prowess
When Rosebud Runner enters, exile the top card of your library. During your next turn, you may play that card from exile.

Rosesworn Knight gets +1/+1 as long as it's embattled. (A creature is embattled if it has a counter on it or a permanent you control attached to it.)

Create a 1/1 green Saproling creature token for each nonland permanent card in your graveyard.

When Rotfeeder Slime dies, you gain 2 life for each creature card in your graveyard.

When Rotting Greatwurm dies, put three +1/+1 counters on target creature you control.
Fleeting {2}{G} (You may cast this spell for its fleeting cost. If you do, sacrifice it at the beginning of the next end step.)

Rouse 4. (Distribute four +1/+1 counters among permanents you control. If they aren't creatures, tap them and they become 0/0 creatures in addition to their other types.)

({T}: Add {R}.)
Rousing Rubble enters tapped.
Double strike
{2}{R}{R}: Rousing Rubble becomes a creature in addition to its other types until end of turn.

Once each turn, when Rova, the Fleshweaver enters or you attack with one or more Horrors, you may put a +1/+1 counter on each creature you control. Then if Rova isn't a token, untap each land you control. Until your next turn, you may cast permanent spells as though they had flash.
{2}{G}{G}, Discard Rova: Create a token that's a copy of Rova, the Fleshweaver, except it's 4/4 and isn't legendary. Activate only as a sorcery.

Whenever Roving Dreadnought attacks, you may salvage a card that was put into your graveyard this turn. (Exile one from your graveyard until this creature leaves the battlefield. Whenever this creature deals combat damage to a player, put a card it salvaged into your hand.)

Gain control of up to two target creatures until end of turn. Untap them. They gain haste until end of turn.
Menagerie — If there are five or more creature types among creatures you control, untap all creatures you control. Until end of turn, they gain “{T}: This creature fights another target creature.”

{T}: Add {C}.
{2}, {T}: Add three mana of any one color.
{3}, {T}: Create a colorless artifact token named Lotus Petal with “{T}, Sacrifice this artifact: Add one mana of any color.”