K-9, Mark I - 537 R WHO

Negative — As long as K-9 is untapped, other legendary creatures you control have ward {1}.
Affirmative — {1}{U}, {T}: Target legendary creature can't be blocked this turn.
Doctor's companion (You can have two commanders if the other is the Doctor.)

rare
Legendary Artifact Creature — Robot Dog
From the Magic: The Gathering set Doctor Who.