Eluge, the Shoreless Sea

Eluge's power and toughness are each equal to the number of Islands you control.
Whenever Eluge enters or attacks, put a flood counter on target land. It's an Island in addition to its other types for as long as it has a flood counter on it.
The first instant or sorcery spell you cast each turn costs {U} (or {1}) less to cast for each land you control with a flood counter on it.

Sol Ring

Arcane Signet

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

Spreading Seas

Enchant land
When Spreading Seas enters, draw a card.
Enchanted land is an Island.