Is Kjeldoran Elite Guard legal in Standard, Modern, and Commander?

Kjeldoran Elite Guard is legal in: Legacy, Vintage, Commander, Pauper.

Kjeldoran Elite Guard

Q: What type of card is Kjeldoran Elite Guard?

Kjeldoran Elite Guard is a Creature — Human Soldier. Its oracle text reads: "{T}: Target creature gets +2/+2 until end of turn. When that creature leaves the battlefield this turn, sacrifice Kjeldoran Elite Guard. Activate only during combat."

Creature — Human Soldier

: Target creature gets +2/+2 until end of turn. When that creature leaves the battlefield this turn, sacrifice Kjeldoran Elite Guard. Activate only during combat.