Prey Upon

Target creature you control fights target creature you don't control. (Each deals damage equal to its power to the other.)

Evolving Wilds

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

Creeping Trailblazer

Other Elementals you control get +1/+0.
{2}{R}{G}: Creeping Trailblazer gets +1/+1 until end of turn for each Elemental you control.

Scampering Scorcher

When Scampering Scorcher enters, create two 1/1 red Elemental creature tokens. Elementals you control gain haste until end of turn. (They can attack and {T} this turn.)

Thunderkin Awakener

Haste
Whenever Thunderkin Awakener attacks, choose target Elemental creature card in your graveyard with toughness less than Thunderkin Awakener's toughness. Return that card to the battlefield tapped and attacking. Sacrifice it at the beginning of the next end step.

Overgrowth Elemental

When Overgrowth Elemental enters, put a +1/+1 counter on another target Elemental you control.
Whenever another creature you control dies, you gain 1 life. If that creature was an Elemental, put a +1/+1 counter on Overgrowth Elemental.

Arboretum Elemental

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Hexproof (This creature can't be the target of spells or abilities your opponents control.)

Mountain

Chandra's Embercat

{T}: Add {R}. Spend this mana only to cast an Elemental spell or a Chandra planeswalker spell.

Feral Invocation

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
Enchanted creature gets +2/+2.

Mask of Immolation

When Mask of Immolation enters, create a 1/1 red Elemental creature token, then attach Mask of Immolation to it.
Equipped creature has "Sacrifice this creature: It deals 1 damage to any target."
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Forest

Chandra, Novice Pyromancer

+1: Elementals you control get +2/+0 until end of turn.
−1: Add {R}{R}.
−2: Chandra, Novice Pyromancer deals 2 damage to any target.

Oakenform

Enchant creature
Enchanted creature gets +3/+3.

Scorch Spitter

Whenever Scorch Spitter attacks, it deals 1 damage to the player or planeswalker it's attacking.