Brazen Collector

First strike
Whenever Brazen Collector attacks, add {R}. Until end of turn, you don't lose this mana as steps and phases end.

Rodeo Pyromancers

Whenever you cast your first spell each turn, add {R}{R}.

Seething Song

Pyretic Ritual

Mountain

Ancient Hellkite

Flying
{R}: Ancient Hellkite deals 1 damage to target creature defending player controls. Activate only if Ancient Hellkite is attacking.

Simian Spirit Guide

Exile Simian Spirit Guide from your hand: Add {R}.

Volcanic Rambler

{2}{R}: Volcanic Rambler deals 1 damage to target player or planeswalker.

Reverberate

Copy target instant or sorcery spell. You may choose new targets for the copy.

Zirilan of the Claw

{1}{R}{R}, {T}: Search your library for a Dragon permanent card, put that card onto the battlefield, then shuffle. That Dragon gains haste until end of turn. Exile it at the beginning of the next end step.

Reckless Barbarian

Sacrifice Reckless Barbarian: Add {R}{R}.

Catalyst Elemental

Sacrifice Catalyst Elemental: Add {R}{R}.

Geosurge

Add {R}{R}{R}{R}{R}{R}{R}. Spend this mana only to cast artifact or creature spells.

Rite of Flame

Add {R}{R}, then add {R} for each card named Rite of Flame in each graveyard.

Furnace Whelp

Flying
{R}: Furnace Whelp gets +1/+0 until end of turn.

Sandstone Needle

Sandstone Needle enters tapped with two depletion counters on it.
{T}, Remove a depletion counter from Sandstone Needle: Add {R}{R}. If there are no depletion counters on Sandstone Needle, sacrifice it.