msem-instigator

When Into the Lion's Den enters, target opponent reveals their hand. You choose a nonland card from it and exile that card until Into the Lion's Den leaves the battlefield.

As Nebula of Empty Gold enters, choose two or three colors. You lose life equal to the number of colors chosen this way.
{T}: Add one mana of any of the chosen colors.

(Add a quest counter as this enters. Sacrifice after 3.)
Whenever you cast a noncreature spell, add a quest counter.
1, 2 — Draw a card, then discard a card.
3 — Return up to two target instant and/or sorcery cards from your graveyard to your hand.
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Vigilance
Whenever a legendary creature you control enters, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Untap each creature you control. After this main phase, there is an additional combat phase followed by an additional main phase. At the beginning of your end step, sacrifice each creature you control that attacked this turn.

Harness (You may tap a creature you control as you cast this spell. If you do, reduce this spell's mana cost by that creature's power.)
Return up to two target cards from your graveyard to your hand. Exile Secret Stash.

Disgraced 5 (This enters with five -1/-1 counters. Whenever it deals combat damage to a player, remove all -1/-1 counters from it.)
Prevent all combat damage that would be dealt to Heir Unapparent.

Whenever Neo-Soul Attendant or another enchantment you control enters, you gain 1 life.

Enchant opponent
When Pathless Shallows enters, exile target creature enchanted player controls until Pathless Shallows leaves the battlefield.
Enchanted player can't cast spells with the same name as the exiled card.

First strike (This creature deals combat damage before creatures without first strike.)
When Attended Knight enters, create a 1/1 white Soldier creature token.

Other Rogues you control have menace.
{2}{U}: Target blocking creature gets -1/-0 until end of turn.

Counter target spell unless its controller pays {1}. If you control a creature with flying, counter that spell unless its controller pays {4} instead.

When you cast this spell, copy it for each color of mana spent to cast it beyond the first.
Flying

Target creature +3/+3 and gains trample until end of turn.
Leitmotif (If you cast this spell from your hand, exile it as it resolves. When you next cast a spell that shares a color with this card, you may cast this from exile without paying its mana cost.)

[+1]: Up to two target creatures you control each get +1/+1 and gain vigilance until end of turn.
[–3]: Create two 1/1 white Dwarf Peasant creature tokens. You gain 2 life.
[–7]: You get an emblem with “Creatures you control get +2/+2 and have double strike.”

Whenever Waketide Serpent attacks, you may pay {2}{U}. If you do, tap target creature. It doesn't untap during its controller's next untap step.

Flying, prowess
When Bound Watcher enters, conjure a card named Data-Point into your hand. (It's a sorcery that costs {2} with “Draw a card.”)

Flying
Sakura Spirit has lifelink as long as it's equipped, enchanted, or has a card inscribed onto it.

As a spell you control is countered by a spell or ability an opponent controls while you control a Mountain, you may reveal Confront the Riddlemaster from your hand. When you do, cast it without paying its mana cost.
This spell can't be countered.
Confront the Riddlemaster deals 4 damage to any target.

Transcend (Activate as a sorcery to gain the next type and a +1/+1 counter.)
You may play an additional land on each of your turns.
{1}{R}{G}: Demigod — Whenever a land you control enters this turn, it deals 3 damage to up to one target creature or planeswalker.
{6}{R}{G}: God — Until end of turn, lands you control become 3/3 Spirit creatures with indestructible and haste that are still lands. Untap them.

Whenever you cast an enchantment spell, you may pay {W}. If you do, put a +1/+1 counter on target creature.

For each basic land type, search your library for a card of that type, then put it onto the battlefield tapped, then shuffle.

Chronicle (As this enters and after your draw step, add a lore counter. Stop after III.)
[Lore I-II] Until your next turn, up to one target creature can't attack or block and its activated abilities can't be activated.
[Lore III] Target opponent skips their next combat phase.

When Terror of the Ontarachie enters, choose one —
• Each player sacrifices a creature.
• Each player loses 5 life.