Marauding Mako

Whenever you discard one or more cards, put that many +1/+1 counters on this creature.
Cycling {2} ({2}, Discard this card: Draw a card.)

Arcane Signet

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

Abandon Attachments

You may discard a card. If you do, draw two cards.

Island

Sol Ring

Sulfur Falls

This land enters tapped unless you control an Island or a Mountain.
{T}: Add {U} or {R}.

Captain Howler, Sea Scourge

Ward—{2}, Pay 2 life.
Whenever you discard one or more cards, target creature gets +2/+0 until end of turn for each card discarded this way. Whenever that creature deals combat damage to a player this turn, you draw a card.

Frantic Search

Draw two cards, then discard two cards. Untap up to three lands.

Counterspell

Reliquary Tower

You have no maximum hand size.
{T}: Add {C}.

Windfall

Each player discards their hand, then draws cards equal to the greatest number of cards a player discarded this way.