Boulder Jockey [Mystery Booster 2 Playtest Cards]

({D} is a land drop. You may give up one potential land drop this turn to pay for {D}.)
Whenever Boulder Jockey attacks, you may pay {D}. If you do, create a 3/3 colorless Construct artifact creature token named Boulder that's tapped and attacking. Sacrifice that token at the beginning of the next end step.