msem-instigator

Target opponent may draw two cards. If they do, you draw four cards. Otherwise, you create four 1/1 red Elemental creature tokens.

Hexproof
Whenever an enchantment you control enters, draw a card.

Whenever you cast an enchantment spell, you may put target creature on the bottom of its owner's library.

This spell costs {1} less to cast for each artifact and/or enchantment you control.
Trample
{1}, Sacrifice another cryptic permanent you control or exile a cryptic card from your graveyard: Put a +1/+1 counter on Observer of Aeons. (Artifacts, enchantments, and modal spells are cryptic.)

Hexproof
Invisible Stalker can't be blocked.

Flash
When Axom enters, remove up to three counters from target permanent.
{2}{U}: Return Axom to its owner's hand.

[+1]: Haide Bankbuster deals 2 damage divided as you choose among one or two targets.
[+1]: Draw two cards unless any player has Haide Bankbuster deal 3 damage to them.
[–9]: Until end of turn, gain control of all permanents target player controls and they gain haste. Untap those permanents.

(As you complete a condition, decode it. After all are decoded, you solve the mystery and transform this.)
When Mystery of the Crashed Craft enters, create two 1/1 red Alien creature tokens with “This creature can't block.”
{MG}—You cast an instant spell.
{MG}—You cast a sorcery spell.

Whenever you cast an instant or sorcery spell, create a 1/1 red Alien creature token with “This creature can't block.”
{2}{R}, Sacrifice two Aliens: Copy target instant or sorcery spell you control. You may choose new targets for the copy.

[+2]: Create a 2/2 red Werewolf creature token with first strike and haste.
[–3]: Tanya deals 3 damage to each creature that's not a Wolf or a Werewolf.
[–8]: For each permanent your opponents control, that player sacrifices it unless they have Tanya deal 2 damage to them.

[+1]: Tanya, the Mooncursed becomes a legendary 3/1 red Werewolf creature with first strike until end of turn.
[–2]: Tanya, the Mooncursed deals 3 damage to target creature or planeswalker.
[–4]: Destroy target nonbasic colorless permanent.

Mountains you control have “{T}: Add {R}{R}.”
[+1]: Exile the top card of your library. You may play that card until the end of your next turn.
[–2]: Conjure six cards named Scorch. Shuffle them and your hand into your library, then draw two cards.

Whenever a player activates an ability that isn't a mana ability, Burning-Tree Shaman deals 1 damage to that player.

Whenever a card is put into a graveyard from anywhere, put a +1/+1 counter on Chief Striking Dawn.
{1}{B}{G}, Remove three counters from Chief Striking Dawn: Return a permanent card from your graveyard to the battlefield.

Whenever Penny and Pete attacks, gain control of up to one target noncreature permanent and up to one target creature until end of turn. Untap the noncreature permanent, then tap the creature. It's attacking.

Each Rogue you control can't be blocked by creatures with greater power than it.
Whenever a Rogue deals combat damage to a player, gain control of target nonland permanent that player controls unless that player pays {1}.

If one or more counters would be put on a permanent you control, you may have that many counters plus one or that many counters minus one put on that permanent instead.

Haste
Whenever Spellslinger Elf deals combat damage to a player, draw a card, then you may cast a card from your hand with mana value 3 or less without paying its mana cost.

Flash
Flying
When Champion of the Provinces enters, return any number of other permanents you control to their owner's hands.

Eureka! (At the beginning of each end step, you get a research counter if you cast a spell this turn. Then if you have eight or more research counters, remove them and create a Masterpiece token of your choice.)
{T}: Draw a card, then discard a card.

Colossal 4—{5}{U}{U}{U} (You may cast this for its colossal cost to have it enter with four +1/+1 counters; or pay {5}{U}{U}{U} as a sorcery: Put four +1/+1 counters on it if it has none.)
Whenever Megalokraken enters or attacks, reveal the top X cards of your library, where X is Megalokraken's power. You may cast a noncreature spell with mana value X or less from among them without paying its mana cost. Put the rest on the bottom of your library in a random order.

Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
Whenever a player activates an ability of an artifact, creature, or land, if it isn't a mana ability, Dedicated Weaponsmith deals 2 damage to that player.

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.)

Whenever Wild Dogs of the Night or another Horror you control enters, exile up to one target card in a graveyard. If that card was a creature card, you gain 2 life and put two +1/+1 counters on that Horror.