msem-instigator

Solar Hatching deals 4 damage to each creature.
Coalesce {6}{R}{R} (You may cast this from your graveyard for {6}{R}{R}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)
When Solar Hatching enters, each player chooses up to two lands they control and sacrifices the rest.

Tap all lands target player controls and that player loses all unspent mana.

Choose one—
• Soul Flame deals X damage to target nonred creature.
• Target red creature gets +X/+0 until end of turn.

Trample, haste
When Soul of the Mountain enters, if it isn't a token, for each two Mountains you control, create a token that's a copy of it.

Advance {2}{R} (Cast this for {2}{R} to advance it as it enters. {2}{R}: Advance this as a sorcery.)
Haste
Whenever Soulblade Warrior advances, it gets +2/+0 until end of turn.

Flying, haste
Whenever you cast an instant or sorcery spell, Sovereign of Old Jidai gets +1/+0 until end of turn.

Exile target creature. That creature's controller reveals cards from the top of their library until they reveal a creature card. That player puts that card onto the battlefield, then shuffles the rest into their library.

Exile the top card of your library. You may have Spark Inspiration deal 2 damage to each opponent. If you don't, you may play that card until end of turn.

Sparkmage Prodigy has first strike as long as it's your turn.
Whenever you cast a cryptic spell, Sparkmage Prodigy deals 1 damage to each opponent. (Artifacts, enchantments, and modal spells are cryptic.)

Haste
When Speaker of the Iris enters, abound. (To abound, you may cast a spell that costs less than this from your hand without paying its mana cost.)
Other creatures you control have haste.

Spearhead deals X damage to target player. (Then exile this card. You may cast the creature later from exile.)

Creatures your opponents control can't block alone. (They can block different creatures.)

Prowess
Whenever you cast a noncreature spell, you may pay {R}. If you do, post a bounty on target creature. (Put a bounty counter on that creature. It has “When this creature dies, each opponent draws a card” as long as it has a bounty counter on it.)

Flip a coin. If you win the flip, draw two cards. Otherwise, discard two cards.

When Speed Reader enters, harmonize. (Trigger up to one harmony of a permanent you control.)
Harmony — Add {R}{R}.

Exile up to three target instant and/or sorcery cards from your graveyard. Until end of turn, you may cast cards exiled this way.
Exile Speedreading.

Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{2}{R}{R}: If an instant or sorcery source you control would deal damage to a permanent or player this turn, it deals that much damage plus 2 instead.

Whenever you cast your second spell each turn, if it's an instant or sorcery spell, you may pay {1}{R}. If you do, gain control of target creature an opponent controls until end of turn. Untap that creature. It gains haste until end of turn.

Spiny Ridge enters tapped. When it does, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this, then you may put that card into your graveyard.)
{T}: Add {R}.
{4}{R}: Spiny Ridge becomes a Lizard creature. (This effect lasts indefinitely.)

Spitfire deals 2 damage to target creature. Up to one target creature you control gets +2/+0 until end of turn.

Haste, prowess
Wanderlust — When Spitfireling enters, if you control four or more differently named lands, create two 1/1 red Elemental creature tokens with prowess and haste.

For each creature you control, put a +1/+1 counter on it or create a Treasure token.

Target creature gets +1/+0 and gains first strike until end of turn.
Draw a card.

Flying, haste
Erratic (When this creature dies, reveal the top four cards of your library. Put a creature card that costs less than this revealed this way onto the battlefield and the rest on the bottom of your library in any order.)
When Splitflame Phoenix dies, you may pay {R}. If you do, return it to its owner's hand.

Flash
When Splitting Image enters, you may pay {2} any number of times. Whenever you do, copy target spell. You may reselect modes and choose new targets for the copies.