Sol Ring

ED-E, Lonesome Eyebot

Flying
ED-E My Love — Whenever you attack, if the number of attacking creatures is greater than the number of quest counters on ED-E, put a quest counter on it.
{2}, Sacrifice ED-E: Draw a card, then draw an additional card for each quest counter on ED-E.

Wasteland Survival Guide

Equipped creature gets +1/+1 for each quest counter among permanents you control.
Equip {1}

Ephemerate

Exile target creature you control, then return it to the battlefield under its owner's control.
Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

Overseer of Vault 76

First Contact — Whenever Overseer of Vault 76 or another creature you control with power 3 or less enters, put a quest counter on Overseer of Vault 76.
At the beginning of combat on your turn, you may remove three quest counters from among permanents you control. When you do, put a +1/+1 counter on each creature you control and they gain vigilance until end of turn.

Quest for Pure Flame

Whenever a source you control deals damage to an opponent, you may put a quest counter on this enchantment.
Remove four quest counters from this enchantment and sacrifice it: If any source you control would deal damage to a permanent or player this turn, it deals double that damage to that permanent or player instead.

Airbender Ascension

When this enchantment enters, airbend up to one target creature.
Whenever a creature you control enters, put a quest counter on this enchantment.
At the beginning of your end step, if this enchantment has four or more quest counters on it, exile up to one target creature you control, then return it to the battlefield under its owner's control.

Monk Gyatso

Whenever another creature you control becomes the target of a spell or ability, you may airbend that creature. (Exile it. While it's exiled, its owner may cast it for {2} rather than its mana cost.)

Personify

Exile target creature you control, then return that card to the battlefield under its owner's control. Create a 1/1 colorless Shapeshifter creature token with changeling. (It's every creature type.)

Mass Hysteria

Firebender Ascension

When this enchantment enters, create a 2/2 red Soldier creature token with firebending 1.
Whenever a creature you control attacking causes a triggered ability of that creature to trigger, put a quest counter on this enchantment. Then if it has four or more quest counters on it, you may copy that ability. You may choose new targets for the copy.

Moira Brown, Guide Author

When Moira Brown enters, create a colorless Equipment artifact token named Wasteland Survival Guide with "Equipped creature gets +1/+1 for each quest counter among permanents you control" and equip {1}.
Whenever you attack, put a quest counter on target nonland permanent you control.

Go Ninja Go

Choose one or both —
• Exile target creature you control, then return it to the battlefield under its owner's control.
• Go Ninja Go deals damage equal to the greatest power among creatures you control to target creature an opponent controls.

Luminarch Ascension

At the beginning of each opponent's end step, if you didn't lose life this turn, you may put a quest counter on this enchantment. (Damage causes loss of life.)
{1}{W}: Create a 4/4 white Angel creature token with flying. Activate only if this enchantment has four or more quest counters on it.

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Zektar Shrine Expedition

Landfall — Whenever a land you control enters, you may put a quest counter on this enchantment.
Remove three quest counters from this enchantment and sacrifice it: Create a 7/1 red Elemental creature token with trample and haste. Exile it at the beginning of the next end step.

Metastatic Evangel

Whenever another nontoken creature you control enters, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Craig Boone, Novac Guard

Reach, lifelink
One for My Baby — Whenever you attack with two or more creatures, put two quest counters on Craig Boone. When you do, Craig Boone deals damage equal to the number of quest counters on it to up to one target creature unless that creature's controller has Craig Boone deal that much damage to them.

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Appa, Steadfast Guardian

Flash
Flying
When Appa enters, airbend any number of other target nonland permanents you control. (Exile them. While each one is exiled, its owner may cast it for {2} rather than its mana cost.)
Whenever you cast a spell from exile, create a 1/1 white Ally creature token.

Sierra, Nuka's Biggest Fan

The Nuka-Cola Challenge — Whenever one or more creatures you control deal combat damage to a player, put a quest counter on Sierra and create a Food token.
Whenever you sacrifice a Food, target creature you control gets +X/+X until end of turn, where X is the number of quest counters on Sierra.

Duchess, Wayward Tavernkeep

Hunters for Hire — Whenever a creature you control deals combat damage to a player, put a quest counter on it.
{1}, Remove a quest counter from a permanent you control: Create a Junk token. (It's an artifact with "{T}, Sacrifice this token: Exile the top card of your library. You may play that card this turn. Activate only as a sorcery.")

Blasphemous Act

This spell costs {1} less to cast for each creature on the battlefield.
Blasphemous Act deals 13 damage to each creature.

Quest for the Holy Relic

Whenever you cast a creature spell, you may put a quest counter on this enchantment.
Remove five quest counters from this enchantment and sacrifice it: Search your library for an Equipment card, put it onto the battlefield, attach it to a creature you control, then shuffle.