Nicol Bolas, Plainswalker

Flying, plainswalk, plainshome (This creature can only attack if defending player controls a plains. At any time, if you control no plains, sacrifice this creature.)
When Nicol Bolas, Plainswalker enters the battlefield, target land becomes a plains until Nicol Bolas leaves the battlefield.
Sacrifice a plains: Regenerate Nicol Bolas. When he regenerates this turn, target land becomes a plains until he leaves the battlefield.