what is the best planeswalker in magic the gathering?
['Nahiri, the Harbinger.', 'Nicol Bolas, Planeswalker.', 'Dack Fayden.', 'Karn Liberated.', 'Gideon, Ally of Zendikar.', 'Ugin, the Spirit Dragon.', 'Liliana of the Veil.', 'Jace, the Mind Sculptor.']