Den of the Bugbear

If you control two or more other lands, Den of the Bugbear enters tapped.
{T}: Add {R}.
{3}{R}: Until end of turn, Den of the Bugbear becomes a 3/2 red Goblin creature with "Whenever this creature attacks, create a 1/1 red Goblin creature token that's tapped and attacking." It's still a land.

Delina, Wild Mage

Whenever Delina, Wild Mage attacks, choose target creature you control, then roll a d20.
1—14 | Create a tapped and attacking token that's a copy of that creature, except it's not legendary and it has "At end of combat, exile this creature."
15—20 | Create one of those tokens. You may roll again.

Mountain

Goblin Morningstar

Equipped creature gets +1/+0 and has trample.
Equip {1}{R}
When Goblin Morningstar enters, roll a d20.
1—9 | Create a 1/1 red Goblin creature token.
10—20 | Create a 1/1 red Goblin creature token, then attach Goblin Morningstar to it.

Hoarding Ogre

Whenever Hoarding Ogre attacks, roll a d20.
1—9 | Create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
10—19 | Create two Treasure tokens.
20 | Create three Treasure tokens.

Zariel, Archduke of Avernus

+1: Creatures you control get +1/+0 and gain haste until end of turn.
0: Create a 1/1 red Devil creature token with "When this creature dies, it deals 1 damage to any target."
−6: You get an emblem with "At the end of the first combat phase on your turn, untap target creature you control. After this phase, there is an additional combat phase."

Barbarian Class

(Gain the next level as a sorcery to add its ability.)
If you would roll one or more dice, instead roll that many dice plus one and ignore the lowest roll.
{1}{R}: Level 2
Whenever you roll one or more dice, target creature you control gets +2/+0 and gains menace until end of turn.
{2}{R}: Level 3
Creatures you control have haste.

Twinshot Sniper

Reach
When Twinshot Sniper enters, it deals 2 damage to any target.
Channel — {1}{R}, Discard Twinshot Sniper: It deals 2 damage to any target.

Swarming Goblins

When Swarming Goblins enters, roll a d20.
1—9 | Create a 1/1 red Goblin creature token.
10—19 | Create two of those tokens.
20 | Create three of those tokens.

Voltage Surge

As an additional cost to cast this spell, you may sacrifice an artifact.
Voltage Surge deals 2 damage to target creature or planeswalker. If this spell's additional cost was paid, Voltage Surge deals 4 damage instead.

Battle Cry Goblin

{1}{R}: Goblins you control get +1/+0 and gain haste until end of turn.
Whenever Battle Cry Goblin attacks, if you attacked with creatures with total power 6 or greater this combat, create a 1/1 red Goblin creature token that's tapped and attacking.

Hulking Bugbear

Ambitious Assault

Creatures you control get +2/+0 until end of turn. If you control a modified creature, draw a card. (Equipment, Auras you control, and counters are modifications.)

Honeymoon Hearse

Trample
Tap two untapped creatures you control: Honeymoon Hearse becomes an artifact creature until end of turn.

Akki War Paint

Enchant artifact or creature
As long as enchanted permanent is a creature, it gets +2/+1.

Raze the Effigy

Choose one —
• Destroy target artifact.
• Target attacking creature gets +2/+2 until end of turn.

You See a Pair of Goblins

Choose one —
• Charge Them — Creatures you control get +2/+0 until end of turn.
• Befriend Them — Create two 1/1 red Goblin creature tokens.