msem-instigator

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.”

When Royal Retriever enters or when a creature scavenges it, you may discard a card. If you do, draw a card.
Scavenge {R} ({R}, Exile this card from your graveyard: Put a number of +1/+1 counters equal to this card's power on target creature. Scavenge only as a sorcery.)

Royster Hounds can't be blocked by creatures with power 2 or less.

Flying
Whenever Rubble Scavenger deals combat damage to a player, you may return target artifact card with mana value 4 or less from your graveyard to the battlefield.

When Rubble Seer enters, you may sacrifice a land or exile a land card from your graveyard. If you do, exile the top card of your library. Until the end of your next turn, you may play that card.

Trample
Rubble Tender's power and toughness are each equal to the number of land cards in your graveyard.
At the beginning of your upkeep, sacrifice a land, then search your library for up to two land cards, put them onto the battlefield tapped, then shuffle.

This spell has flash as long as you control a creature with power 4 or greater.
Target creature you control deals damage equal to its power to target creature you don't control.

{T}: Add {C}.
{2}, {T}, Sacrifice Rugged Expanse: Put a +1/+1 counter on target creature. It gains vigilance until end of turn. Activate only as a sorcery.

Choose target creature, then choose two —
• The chosen creature gets +3/+0 until end of turn.
• The chosen creature gains trample until end of turn.
• The chosen creature gains first strike until end of turn.