Underground River

{T}: Add {C}.
{T}: Add {U} or {B}. This land deals 1 damage to you.

Watery Grave

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

Whenever a creature you control deals combat damage to a player, that player discards a card.

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

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

At the beginning of each end step, if an opponent lost 3 or more life this turn, you may draw a card. (Damage causes loss of life.)

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

All creatures have "At the beginning of your upkeep, sacrifice this creature unless you pay 1 life."

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

Whenever a creature attacks you, its controller loses 1 life.

Whenever a creature you control deals combat damage to a player, you may draw a card.
Cycling {2} ({2}, Discard this card: Draw a card.)

If you would draw a card except the first one you draw in each of your draw steps, draw two cards instead.

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