Drowned Catacomb

Drowned Catacomb enters tapped unless you control an Island or a Swamp.
{T}: Add {U} or {B}.

Arcane Signet

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

Morphic Pool enters tapped unless you have two or more opponents.
{T}: Add {U} or {B}.

{T}: Add {C}.
{1}, {T}, Sacrifice Mind Stone: Draw a card.

{T}, Pay 1 life, Sacrifice Polluted Delta: Search your library for an Island or Swamp card, put it onto the battlefield, then shuffle.

{T}: Add {U}.
{T}: Add {B}. Activate only if you control an Island or a Swamp.

{T}: Add {C}.
{U/B}, {T}: Add {U}{U}, {U}{B}, or {B}{B}.

{T}, Pay 1 life, Sacrifice Prismatic Vista: Search your library for a basic land card, put it onto the battlefield, then shuffle.

{T}: Add {C}.
{T}: Add {U} or {B}. Underground River deals 1 damage to you.

Shipwreck Marsh enters tapped unless you control two or more other lands.
{T}: Add {U} or {B}.

({T}: Add {U} or {B}.)
As Watery Grave enters, you may pay 2 life. If you don't, it enters tapped.