msem-instigator

Golden age (If you cast an instant or sorcery spell, activated a nonmana ability, and attacked this turn, enter a renaissance for this game.)
Search your library for up to three creature cards with different mana values 4 or less, reveal them, put them into your hand, then shuffle. If you're in a renaissance, you may put one of those cards onto the battlefield instead of into your hand.

Trample
Savage Mammoth gets +1/+1 for each land you control.
Ride {4}{G} ({4}{G}: Transform this and attach it to target creature you control without a Steed. Ride only as a sorcery.)

When Savage Savant enters, create a 4/4 green Beast creature token.

Vigilance
Cat creatures you control have vigilance.
When Savannah Scout enters, create a 2/2 white Cat creature token.

Untap all creatures and lands you control during each other player's untap step.
Ascend {4}{R}{R}{R} ({4}{R}{R}{R}: Exile this creature, then return it to the battlefield transformed. Ascend only as a sorcery.)

Lionize {1}{W} ({1}{W}, Exile this card from your hand: Put a +1/+1 counter on target creature and it gains the following abilities until end of turn. You may cast this card on a later turn from exile.)
Flying
Other creatures you control get +1/+1.

Enchant creature
Enchanted creature gets +4/+4 and has trample.
When enchanted creature dies, create a 4/4 green Beast creature token with trample.

{3}{G}: Scaled Devestator gets +1/+1 and gains trample until end of turn.

When Scaled Lurker enters, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.

{R}, Discard a card: Target creature blocking Scaled Mindreaver gains winnow until end of turn. (Damage dealt to it also causes its controller to lose that much life.)

Poisonous 4 (Whenever this creature deals combat damage to a player, that player gets four poison counters.)
At the beginning of combat on each of your turns, if an opponent is poisoned, creatures you control gain trample until end of turn.

Prowess
Whenever you cast a noncreature spell, create a 3/3 red Dragon creature token with flying.

Counter target spell. Tap all lands that spell's controller controls and that player loses all unspent mana.

Flying
Whenever Scavenging Hilakites attacks, you may sacrifice another creature. When you do, Scavenging Hilakites deals damage equal to the sacrificed creature's power to any target.

Reach
When Scavenging Pack enters, you may destroy target artifact with mana value 2 or less.

Draw three cards, then manifest a card from your hand. (To manifest a card, put it onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.)

Whenever one or more nontoken Merfolk you control attack, create a 2/1 red Merfolk creature token.

Menace
When Scion of Calamities enters, exile the top two cards of your library. Until the end of your next turn, you may play one of those cards.
Whenever a Mountain you control enters, you may aetherize Scion of Calamities. (To aetherize, create a token that's a copy of it, then exile that token.)

Deathtouch
When Scion of Desolation enters, put target creature card with mana value 3 or less from a graveyard onto the battlefield under your control.
Whenever a Swamp you control enters, you may aetherize Scion of Desolation. (To aetherize, create a token that's a copy of it, then exile that token.)

Trample
When Scion of Flourishing enters, put a +1/+1 counter on each other creature you control. Those creatures gain trample until end of turn.
Whenever a Forest you control enters, you may aetherize Scion of Flourishing. (To aetherize, create a token that's a copy of it, then exile that token.)

When Scion of Sarrithaz enters, create a 2/2 black Zombie creature token.
{2}{B}, Sacrifice a creature: Draw a card.

Vigilance
When Scion of Storms enters, create a 2/2 white Elemental creature token with flying.
Whenever a Plains you control enters, you may aetherize Scion of Storms. (To aetherize, create a token that's a copy of it, then exile that token.)

Flying
When Scion of Torrents enters, you may return target nonland permanent to its owner's hand.
Whenever an Island you control enters, you may aetherize Scion of Torrents. (To aetherize, create a token that's a copy of it, then exile that token.)

First strike
Whenever Scion of the Pack enters or one or more creatures you control deal combat damage to an opponent or planeswalker, create a 2/2 green Hound creature token.

Scion of the Wild's power and toughness are each equal to the number of creatures you control.