Mardu Ascendancy

Whenever a nontoken creature you control attacks, create a 1/1 red Goblin creature token that's tapped and attacking.
Sacrifice Mardu Ascendancy: Creatures you control get +0/+3 until end of turn.

Khans of Tarkir

Whenever a nontoken creature you control attacks, put a 1/1 red Goblin creature token onto the battlefield tapped and attacking.
Sacrifice Mardu Ascendancy: Creatures you control get +0/+3 until end of turn.

Khans of Tarkir Promos

Although the tokens are attacking, they were never declared as attacking creatures (for purposes of abilities that trigger whenever a creature attacks, for example).

As the Goblin token enters the battlefield, you choose which opponent or opposing planeswalker it’s attacking. It doesn’t have to attack the same opponent or opposing planeswalker that the original creature is attacking.