Enter the Enigma

Target creature can't be blocked this turn.
Draw a card.

Ninja of the Deep Hours

Ninjutsu {1}{U} ({1}{U}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever Ninja of the Deep Hours deals combat damage to a player, you may draw a card.

Yuriko, the Tiger's Shadow

Commander ninjutsu {U}{B} ({U}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand or the command zone tapped and attacking.)
Whenever a Ninja you control deals combat damage to a player, reveal the top card of your library and put that card into your hand. Each opponent loses life equal to that card's mana value.

Counterspell

Prosperous Thief

Ninjutsu {1}{U} ({1}{U}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever one or more Ninja or Rogue creatures you control deal combat damage to a player, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Thousand-Faced Shadow

Ninjutsu {2}{U}{U} ({2}{U}{U}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Flying
When Thousand-Faced Shadow enters from your hand, if it's attacking, create a token that's a copy of another target attacking creature. The token enters tapped and attacking.

Kaito, Cunning Infiltrator

Whenever a creature you control deals combat damage to a player, put a loyalty counter on Kaito.
+1: Up to one target creature you control can't be blocked this turn. Draw a card, then discard a card.
−2: Create a 2/1 blue Ninja creature token.
−9: You get an emblem with "Whenever a player casts a spell, you create a 2/1 blue Ninja creature token."

Nashi, Moon Sage's Scion

Ninjutsu {3}{B} ({3}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever Nashi, Moon Sage's Scion deals combat damage to a player, exile the top card of each player's library. Until end of turn, you may play one of those cards. If you cast a spell this way, pay life equal to its mana value rather than paying its mana cost.

Mockingbird

Flying
You may have Mockingbird enter as a copy of any creature on the battlefield with mana value less than or equal to the amount of mana spent to cast Mockingbird, except it's a Bird in addition to its other types and it has flying.

Roaming Throne

Ward {2}
As Roaming Throne enters, choose a creature type.
Roaming Throne is the chosen type in addition to its other types.
If a triggered ability of another creature you control of the chosen type triggers, it triggers an additional time.

Kaito, Bane of Nightmares

Ninjutsu {1}{U}{B} ({1}{U}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
During your turn, as long as Kaito has one or more loyalty counters on him, he's a 3/4 Ninja creature and has hexproof.
+1: You get an emblem with "Ninjas you control get +1/+1."
0: Surveil 2. Then draw a card for each opponent who lost life this turn.
−2: Tap target creature. Put two stun counters on it.

Changeling Outcast

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

Flare of Denial

You may sacrifice a nontoken blue creature rather than pay this spell's mana cost.
Counter target spell.

Silver-Fur Master

Ninjutsu {U}{B} ({U}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Ninjutsu abilities you activate cost {1} less to activate.
Other Ninja and Rogue creatures you control get +1/+1.

Mistblade Shinobi

Ninjutsu {U} ({U}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever Mistblade Shinobi deals combat damage to a player, you may return target creature that player controls to its owner's hand.

Siren Stormtamer

Flying
{U}, Sacrifice Siren Stormtamer: Counter target spell or ability that targets you or a creature you control.