Is K-9, Mark I legal in Standard, Modern, and Commander?

K-9, Mark I is legal in: Legacy, Vintage, Commander.

What type of card is K-9, Mark I?

K-9, Mark I is a Legendary Artifact Creature — Robot Dog. Its oracle text reads: "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.) Power/Toughness: 1/1"