Squirrel

{1}, {T}, Sacrifice this artifact: Target creature you control explores. Activate only as a sorcery. (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 that creature, then put the card back or put it into your graveyard.)

Saproling

Germ

Pegasus

Marit Lage

Thundertrap Trainer

When this creature enters, look at the top four cards of your library. You may reveal a noncreature, nonland card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.
(This token's mana cost is {1}{U}.)

Servo

Spirit

Ooze

Inkling

Bird

Night

As it becomes night, transform all daybound permanents.
Permanents enter the battlefield nightbound.
If a player casts at least two spells during their own turn, it becomes day next turn.

(If it becomes day or night or if a daybound permanent enters the battlefield, track day/night for the rest of the game.)
As it becomes day, transform all nightbound permanents.
If a player casts no spells during their own turn, it becomes night next turn.

Day // Night

Wolf

Plant

Drake

Eldrazi Scion

Harpy

Sheep

Human Soldier

Wurm

Spider

Treasure

{T}, Sacrifice this token: Add one mana of any color.

Shapeshifter

Changeling (This token is every creature type.)
Deathtouch

Faerie Dragon

Copy

(This token can be used to represent a token that's a copy of a permanent.)

The Initiative

Whenever one or more creatures a player controls deal combat damage to you, that player takes the initiative.
Whenever you take the initiative and at the beginning of your upkeep, venture into Undercity. (If you're in a dungeon, advance to the next room. If you're not, enter Undercity. You can take the initiative even if you already have it.)

Undercity

You can't enter this dungeon unless you "venture into Undercity."
Secret Entrance — Search your library for a basic land card, reveal it, put it into your hand, then shuffle. (Leads to: Forge, Lost Well)
Forge — Put two +1/+1 counters on target creature. (Leads to: Trap!, Arena)
Lost Well — Scry 2. (Leads to: Arena, Stash)
Trap! — Target player loses 5 life. (Leads to: Archives)
Arena — Goad target creature. (Leads to: Archives, Catacombs)
Stash — Create a Treasure token. (Leads to: Catacombs)
Archives — Draw a card. (Leads to: Throne of the Dead Three)
Catacombs — Create a 4/1 black Skeleton creature token with menace. (Leads to: Throne of the Dead Three)
Throne of the Dead Three — Reveal the top ten cards of your library. Put a creature card from among them onto the battlefield with three +1/+1 counters on it. It gains hexproof until your next turn. Then shuffle.

Undercity // The Initiative

Treefolk

Tarmogoyf

Tarmogoyf's power is equal to the number of card types among cards in all graveyards and its toughness is equal to that number plus 1.

Zombie Army

Goblin

Demon

Cat Soldier

Faerie

Elephant

Manifest

(You can cover a face-down manifested creature with this reminder card.
A manifested creature card can be turned face up any time for its mana cost. A face-down card can also be turned face up for its morph cost.)

Robot

Changeling (This token is every creature type.)

Kobolds of Kher Keep

Insect

Vigilance
Whenever you draw a card, put a +1/+1 counter on this creature.

Monk

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

Food

{2}, {T}, Sacrifice this token: You gain 3 life.

Dinosaur

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)

Thopter

Orc Army

Clue

{2}, Sacrifice this artifact: Draw a card.

Clue // Clue

Cat Beast

The Monarch

At the beginning of your end step, draw a card.
Whenever a creature deals combat damage to you, its controller becomes the monarch.

Squid

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)

Sliver

Dragon

Zombie

Bear

Soldier

Elemental

Construct

Knight

Frog Lizard

Gold

Sacrifice this token: Add one mana of any color.

Gnome

Beast

Tentacle

Worm

Eldrazi Spawn

Ogre

Vampire

Snake

Faerie Rogue

Human

Human // Wolf

Angel

Gnome Soldier

This creature's power and toughness are each equal to the number of artifacts and/or creatures you control.

Rukh

Warrior

Assassin

Elf Warrior

Angel // Demon

Thrull

This creature's power and toughness are each equal to the number of creatures you control.

Octopus

Timeless Witness

When Timeless Witness enters the battlefield, return target card from your graveyard to your hand.

Goblin Soldier

Lifelink (Damage dealt by this creature also causes you to gain that much life.)