Hidden Volcano

Hidden Volcano enters tapped.
{T}: Add {R}.
{4}{R}, {T}, Sacrifice Hidden Volcano: Discover 4. Activate only as a sorcery. (Exile cards from the top of your library until you exile a nonland card with mana value 4 or less. Cast it without paying its mana cost or put it into your hand. Put the rest on the bottom in a random order.)

Thunderous Wrath

Thunderous Wrath deals 5 damage to any target.
Miracle {R} (You may cast this card for its miracle cost when you draw it if it's the first card you drew this turn.)

Gargadon

Trample
Suspend 4—{1}{R} (Rather than cast this card from your hand, you may pay {1}{R} and exile it with four time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost. It has haste.)

Fiery Fall

Fiery Fall deals 5 damage to target creature.
Basic landcycling {1}{R} ({1}{R}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

Mountain

Canyon Lurkers

Morph {3}{R} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Runaway Boulder

Flash
When Runaway Boulder enters, it deals 6 damage to target creature an opponent controls.
Cycling {2} ({2}, Discard this card: Draw a card.)

Erratic Explosion

Choose any target. Reveal cards from the top of your library until you reveal a nonland card. Erratic Explosion deals damage equal to that card's mana value to that permanent or player. Put the revealed cards on the bottom of your library in any order.

Dwarven Mine

({T}: Add {R}.)
Dwarven Mine enters tapped unless you control three or more other Mountains.
When Dwarven Mine enters untapped, create a 1/1 red Dwarf creature token.

Blitz Automaton

Prototype {2}{R} — 3/2 (You may cast this spell with different mana cost, color, and size. It keeps its abilities and types.)
Haste

Oxidda Golem

Affinity for Mountains (This spell costs {1} less to cast for each Mountain you control.)
Haste

Riddle of Lightning

Choose any target. Scry 3, then reveal the top card of your library. Riddle of Lightning deals damage equal to that card's mana value to that permanent or player.