Energy Reserve

Brotherhood Scribe

Metalcraft — {T}: You get {E} (an energy counter). Activate only if you control three or more artifacts.
Whenever you get one or more {E} during your turn, creatures you control get +1/+1 until end of turn.

Codsworth, Handy Helper

Commanders you control have ward {2}.
{T}: Add {W}{W}. Spend this mana only to cast Aura and/or Equipment spells.
{T}: Attach target Aura or Equipment you control to target creature you control. Activate only as a sorcery.

Junk

Commander Sofia Daguerre

Flash
Crash Landing — When Commander Sofia Daguerre enters, destroy up to one target legendary permanent. That permanent's controller creates 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.")

Copy

Gary Clone

Squad {2} (As an additional cost to cast this spell, you may pay {2} any number of times. When this creature enters, create that many tokens that are copies of it.)
Whenever this creature attacks, each creature you control named Gary Clone gets +1/+0 until end of turn.

Idolized

Enchant creature
Enchanted creature has "Whenever this creature attacks alone, it gets +X/+X until end of turn, where X is the number of nonland permanents you control."

Clue

Overencumbered

Food

Enchant opponent
When this Aura enters, enchanted opponent creates a Clue token, a Food token, and a Junk token.
At the beginning of combat on enchanted opponent's turn, that player may pay {1} for each artifact they control. If they don't, creatures can't attack this combat.

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.

Paladin Danse, Steel Maverick

Vigilance, lifelink
Exile Paladin Danse: Each creature you control that's an artifact or Human gains indestructible until end of turn.

Pre-War Formalwear

When this Equipment enters, return target creature card with mana value 3 or less from your graveyard to the battlefield and attach this Equipment to it.
Equipped creature gets +2/+2 and has vigilance.
Equip {3}

Treasure

Bottle-Cap Blast

Improvise (Your artifacts can help cast this spell. Each artifact you tap after you're done activating mana abilities pays for {1}.)
Bottle-Cap Blast deals 5 damage to any target. If excess damage was dealt to a permanent this way, create that many tapped Treasure tokens. (They're artifacts with "{T}, Sacrifice this token: Add one mana of any color.")

Human Knight

The Prydwen, Steel Flagship

Flying
Whenever another nontoken artifact you control enters, create a 2/2 white Human Knight creature token with "This token gets +2/+2 as long as an artifact entered the battlefield under your control this turn."
Crew 2

Securitron Squadron

Squad {3} (As an additional cost to cast this spell, you may pay {3} any number of times. When this creature enters, create that many tokens that are copies of it.)
Vigilance
Whenever a creature token you control enters, put a +1/+1 counter on it.

Sentry Bot

Flash
This spell costs {1} less to cast for each creature attacking you.
When this creature enters, you get {E} for each creature attacking you.
At the beginning of combat on your turn, you may pay {E}{E}{E}. If you do, put a +1/+1 counter on each creature you control.

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.

Vault 13: Dweller's Journey

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — For each player, exile up to one other target enchantment or creature that player controls until this Saga leaves the battlefield.
II — You gain 2 life and scry 2.
III — Return two cards exiled with this Saga to the battlefield under their owners' control and put the rest on the bottom of their owners' libraries.

Vault 75: Middle School

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Exile all creatures with power 4 or greater.
II, III — Put a +1/+1 counter on each creature you control.

Fallout