Have

Satoru Umezawa

Whenever you activate a ninjutsu ability, look at the top three cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order. This ability triggers only once each turn.
Each creature card in your hand has ninjutsu {2}{U}{B}.

Dimir Signet

Changeling Outcast

Changeling (This card is every creature type.)
Changeling Outcast can't block and can't be blocked.

Island

Arcane Signet

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

Command Tower

Sunken Hollow

({T}: Add {U} or {B}.)
Sunken Hollow enters tapped unless you control two or more basic lands.

Counterspell

Reliquary Tower

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

Choked Estuary

As Choked Estuary enters, you may reveal an Island or Swamp card from your hand. If you don't, Choked Estuary enters tapped.
{T}: Add {U} or {B}.