Mando, The Mercenary

Vigilance, Double Strike, First Strike
If a planeswalker is on the battlefield, gain +2/+2 and indestructible.
If Mando, The Mercenary destroys a planeswalker, gain +4/+4 and indestructible permanently.
When Mando, The Mercenary dies, put it into your library instead of in the graveyard, it cost {2} more.