{T}: Add one mana of any color in your commander's color identity.
{1}{U}
Brineborn Cutthroat
Creature - Merfolk Pirate
Flash (You may cast this spell any time you could cast an instant.)
Whenever you cast a spell during an opponent's turn, put a +1/+1 counter on Brineborn Cutthroat.
2 /
1
--
Command Tower
Land
{T}: Add one mana of any color in your commander's color identity.
{U}{U}
Counterspell
Instant
Counter target spell.
{U}{B}
Countersquall
Instant
Counter target noncreature spell. Its controller loses 2 life.
{U/B}{U/B}
Cunning Nightbonder
Creature - Human Rogue
Flash
Spells with flash you cast cost {1} less to cast and can't be countered.
2 /
2
{U}{B}
Drown in the Loch
Instant
Choose one --
• Counter target spell with mana value less than or equal to the number of cards in its controller's graveyard.
• Destroy target creature with mana value less than or equal to the number of cards in its controller's graveyard.
{2}{B}
Faerie Tauntings
Tribal Enchantment - Faerie
Whenever you cast a spell during an opponent's turn, you may have each opponent lose 1 life.
{4}{U}{B}
Lochmere Serpent
Creature - Serpent
Flash
{U}, Sacrifice an Island: Lochmere Serpent can't be blocked this turn.
{B}, Sacrifice a Swamp: You gain 1 life and draw a card.
{U}{B}: Exile five target cards from an opponent's graveyard. Return Lochmere Serpent from your graveyard to your hand. Activate only as a sorcery.
7 /
7
{3}{U}
Mystical Teachings
Instant
Search your library for an instant card or a card with flash, reveal it, put it into your hand, then shuffle.
Flashback {5}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)
{2}{U}
Naiad of Hidden Coves
Enchantment Creature - Nymph
As long as it's not your turn, spells you cast cost {1} less to cast.
2 /
3
{3}{U}{B}
Nymris, Oona's Trickster
Legendary Creature - Faerie Knight
Flash
Flying
Whenever you cast your first spell during each opponent's turn, look at the top two cards of your library. Put one of those cards into your hand and the other into your graveyard.
1 /
6
{2}{U}{U}
Overcharged Amalgam
Creature - Zombie Horror
Flash
Flying
Exploit (When this creature enters the battlefield, you may sacrifice a creature.)
When Overcharged Amalgam exploits a creature, counter target spell, activated ability, or triggered ability.
3 /
3
{2}{U}
Portal Mage
Creature - Human Wizard
Flash
When Portal Mage enters the battlefield during the declare attackers step, you may reselect which player or planeswalker target attacking creature is attacking. (It can't attack its controller or its controller's planeswalkers.)
2 /
2
--
Reliquary Tower
Land
You have no maximum hand size.
{T}: Add {C}.
{2}{U}{U}
Rewind
Instant
Counter target spell. Untap up to four lands.
{U}{B}{B}
Slitherwisp
Creature - Elemental Nightmare
Flash
Whenever you cast another spell that has flash, you draw a card and each opponent loses 1 life.
3 /
2
{2}
Thought Vessel
Artifact
You have no maximum hand size.
{T}: Add {C}.
{2}{U}
Unwind
Instant
Counter target noncreature spell. Untap up to three lands.
{3}{U}{U}
Voracious Greatshark
Creature - Shark
Flash
When Voracious Greatshark enters the battlefield, counter target artifact or creature spell.
5 /
4
{U}
Wash Away
Instant
Cleave {1}{U}{U} (You may cast this spell for its cleave cost. If you do, remove the words in square brackets.)
Counter target spell [that wasn't cast from its owner's hand].
{2}{U}
Wavebreak Hippocamp
Enchantment Creature - Horse Fish
Whenever you cast your first spell during each opponent's turn, draw a card.