Surtland Elementalist

As an additional cost to cast this spell, reveal a Giant card from your hand or pay {2}.
Whenever Surtland Elementalist attacks, you may cast an instant or sorcery spell from your hand without paying its mana cost.

Aegar, the Freezing Flame

Whenever a creature or planeswalker an opponent controls is dealt excess damage, if a Giant, Wizard, or spell you controlled dealt damage to it this turn, draw a card.

Wizards of Thay

Myriad (Whenever this creature attacks, for each opponent other than defending player, you may create a token that's a copy of this creature that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)
Instant and sorcery spells you cast cost {1} less to cast.
You may cast sorcery spells as though they had flash.

Of One Mind

This spell costs {2} less to cast if you control a Human creature and a non-Human creature.
Draw two cards.

Wizard's Retort

This spell costs {1} less to cast if you control a Wizard.
Counter target spell.

Mystical Dispute

This spell costs {2} less to cast if it targets a blue spell.
Counter target spell unless its controller pays {3}.

Cyclone Summoner

When Cyclone Summoner enters the battlefield, if you cast it from your hand, return all permanents to their owners' hands except for Giants, Wizards, and lands.

Out of Air

This spell costs {2} less to cast if it targets a creature spell.
Counter target spell.

Calamity Bearer

If a Giant source you control would deal damage to a permanent or player, it deals double that damage to that permanent or player instead.

Quakebringer

Your opponents can't gain life.
At the beginning of your upkeep, Quakebringer deals 2 damage to each opponent. This ability triggers only if Quakebringer is on the battlefield or if Quakebringer is in your graveyard and you control a Giant.
Foretell {2}{R}{R}

Tectonic Giant

Whenever Tectonic Giant attacks or becomes the target of a spell an opponent controls, choose one —
• Tectonic Giant deals 3 damage to each opponent.
• Exile the top two cards of your library. Choose one of them. Until the end of your next turn, you may play that card.

Sapphire Medallion

Blue spells you cast cost {1} less to cast.

Frostpyre Arcanist

This spell costs {1} less to cast if you control a Giant or a Wizard.
When Frostpyre Arcanist enters the battlefield, search your library for an instant or sorcery card with the same name as a card in your graveyard, reveal it, put it into your hand, then shuffle.

Thryx, the Sudden Storm

Flash
Flying
Spells you cast with mana value 5 or greater cost {1} less to cast and can't be countered.

Warchief Giant

Haste
Myriad (Whenever this creature attacks, for each opponent other than defending player, you may create a token that's a copy of this creature that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)

Ertai's Scorn

This spell costs {U} less to cast if an opponent cast two or more spells this turn.
Counter target spell.