Naiad of Hidden Coves

During turns other than yours, spells you cast cost {1} less to cast.

Unwind

Counter target noncreature spell. Untap up to three lands.

Urza's Ruinous Blast

(You may cast a legendary sorcery only if you control a legendary creature or planeswalker.)
Exile all nonland permanents that aren't legendary.

Raff Capashen, Ship's Mage

Flash
Flying
You may cast historic spells as though they had flash. (Artifacts, legendaries, and Sagas are historic.)

Azorius Signet

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Sol Ring

Seat of the Synod

Talisman of Progress

{T}: Add {C}.
{T}: Add {W} or {U}. Talisman of Progress deals 1 damage to you.

Wavebreak Hippocamp

Whenever you cast your first spell during each opponent's turn, draw a card.

Karn's Temporal Sundering

(You may cast a legendary sorcery only if you control a legendary creature or planeswalker.)
Target player takes an extra turn after this one. Return up to one target nonland permanent to its owner's hand. Exile Karn's Temporal Sundering.