msem-instigator

Create a Treasure token.
Showcase {2}{R} (Then if you cast this for its showcase cost, create a 1/1 red Bard creature token that can't block and exile this. Whenever it attacks, you may cast a free copy of this.)

Gain control of target creature until end of turn. Untap that creature. It gains haste until end of turn.

Target creature gets +2/+1 and gains trample until end of turn. Create a tapped Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

Bulwark — {2}{G}: Stronghold Recruit gets +2/+2 until end of turn. Activate only once each turn and only if you control a creature with toughness 4 or greater.

Whenever another Warrior creature you control attacks, you may return Stubborn Blademate from your graveyard to the battlefield tapped and attacking. If you do, sacrifice it at end of combat.

Defender
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
{T}: Student of Lightning deals damage equal to its power to target player.

Whenever Student of the Coil attacks, target creature gains poisonous 1 until end of turn. (Whenever that creature deals combat damage to a player, that player gets a poison counter.)

Improve {G} ({G}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
Whenever an Elf you control dies, you may search your library for a land card, reveal it, put it into your hand, then shuffle.

If you've lost life this turn, you may cast this spell as though it had flash.
Return X target cards with different mana values from your graveyard to your hand. Put Studies Past on the bottom of its owner's library.

Search your library for up to two creature cards and reveal them, then shuffle. Put one on the bottom of your library and the rest on top.

Stunning Cascade enters the battlefield tapped.
{T}: Add {U} or {R}.
{2}{U}{R}, {T}, Sacrifice Stunning Cascade: Draw a card.

Renown 1 (When this creature deals combat damage to a player, if it isn't renowned, put a +1/+1 counter on it and it becomes renowned.)
Whenever a creature you control becomes renowned, you may have it fight target creature you don't control. (Each deals damage equal to its power to the other.)

At the beginning of combat on your turn, if you control six or more lands, put a +1/+1 counter on target creature you control.

As Sturdy Outpost enters the battlefield, you may pay 3 life. If you don't, it enters the battlefield tapped.
{T}: Add {G}, {W}, or {U}.

Concord — At the beginning of combat on your turn, if there are four or more card types among permanents you control, Sturdyshell Hammerclaw gets +2/+1 and gains trample until end of turn.

({T}: Add {B}.)
As Stygian Dunes enters the battlefield, you may pay 1 life. If you don't, Stygian Dunes enters the battlefield tapped.

Substack Ports enters the battlefield tapped.
{T}: Add {U} or {B}.
{U}{B}, {T}, Sacrifice Substack Ports: Conjure a card named Data-Point into your hand. (It's a sorcery that costs {2} with “Draw a card.”)

Breach (Whenever this deals combat damage to a player, you may have it become an Aura Curse until your next turn. Attach it to that player.)
At the beginning of your end step, Substack Sniper deals 1 damage to you and to each cursed opponent.

When Suburban Runebrawler enters the battlefield, exile target instant or sorcery card with mana value 2 or less from your graveyard.
Landfall — Once each turn, when a land enters the battlefield under your control, you may cast a copy of the exiled card without paying its mana cost.

Subway Shambler can't be blocked by creatures with lesser power.
At the beginning of each end step, if you're horrific, put a +1/+1 counter on Subway Shambler. (You're horrific as long as you've sacrificed a permanent or discarded a card this turn.)

Tithe (As you cast this spell, you may tap three artifacts and/or creatures you control.)
You may cast this spell as though it had flash if its tithe is paid.
Gain control of target creature until end of turn. Untap that creature. It gains haste until end of turn.

Target creature can't block this turn.
Inscribe {1}{R} ({1}{R}: Exile this card from your hand inscribed on a creature you control. Whenever that creature attacks, its controller may cast a copy of the inscribed card without paying its mana cost. Inscribe only as a sorcery.)

As an additional cost to cast this spell, put a -1/-1 counter on a creature you control.
Search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle.

Trample, haste
Whenever Sugon, Destruction's Fist deals combat damage to a player, return it to its owner's hand unless you have Sugon deal 5 damage to you.

Flying
Suisei the Southern Star gets +1/+1 for each comet counter you have.
Whenever you cast an instant or sorcery spell with mana value greater than the number of comet counters you have, you may pay {R}. If you do, return Suisei from your graveyard to the battlefield, then you get a comet counter.