Channel time magic, casting and flashing back noncreature spells.

Whenever a creature the heroes control dies, the heroes lose 1 life.

Gain experience with Katara

Small humanoid (kobold), Challenge 1/8
Armor class 12, Hit Points 5
Speed 30 ft.
Attacks Dagger, Sling
STR 7 (-2) DEX 15 (+2) CON 9 (-1)
INT 8 (-1) WIS 7 (-2) CHA 8 (-1)

The bosses play an additional card each turn.
At the start of the Boss turn, the bosses lose 2 life.

Channel Avatar Kyoshi

, Sacrifice this artifact: This artifact deals 2 damage to target attacking creature without flying.

, , Sacrifice this token: Search your library for a basic land card, put it onto the battlefield tapped, then
shuffle.

Take a lesson on earthbending

When this boss enters, the bosses gain 5 life for each boss in play.

Learn to get stronger

Maximize Black Widow's deadly skill by granting deathtouch to your creatures.

Fill your library

Cave Entrance — Scry 1. (=> Goblin Lair or Mine Tunnels)

Goblin Lair — Create a 1/1 red Goblin creature token. (=> Storeroom or Dark Pool)

Mine Tunnels — Create a Treasure token. (=> Dark Pool or Fungi Cavern)

Storeroom — Put a +1/+1 counter on target creature. (=> Temple of Dumathoin)

Dark Pool — Each opponent loses 1 life and you gain 1 life. (=> Temple of Dumathoin)

Fungi Cavern — Target creature gets -4/-0 until your next turn. (=> Temple of Dumathoin)

Temple of Dumathoin — Draw a card.

, Sacrifice this token: Add three mana of any one color.

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 or disguise cost.

Large monstrosity, Challenge 3
Armor class 14, Hit Points 68
Speed 30 ft., fly 50 ft.
Attacks Bite, Claw, Tail Spike
STR 17 (+3) DEX 16 (+3) CON 17 (+3)
INT 7 (-2) WIS 12 (+1) CHA 8 (-1)

, , Sacrifice this artifact: Target creature you control explores. Activate only as a sorcery.

Large construct (inevitable), Challenge 25
Armor Class 22, Hit Points 432
Speed 40 ft., fly 30 ft. (hover)
Attacks Innate Spellcasting, Unerring Slam, Blazing Edict, Justify
STR 28 (+9) DEX 12 (+1) CON 26 (+8)
INT 19 (+4) WIS 15 (+2) CHA 18 (+4)