Karns popular in Mono Black control in Modern and Tron decks wherever theyre found, and we can assume these reprints with special borders will be worth a tad more than its average cost
There's no way of knowing if you'll find the most valuable Magic: The Gathering card until you start looking around, especially considering that at the end of the day
This is also a very aggressive planeswalker design, so it defends itself fairly poorly you cant simply cast Chandra and remove a threat, a near-and-dear ability for playable walkers
More mana income is good, but theres always the risk of overdoing it
A well-timed Mana Drain can pull you so far ahead in value that an opponent could never hope to catch up
The Emerald cards give you plenty of indirect ways to mess up your opponent's plans, meaning that this is a slow-burn deck where every play counts if you want to win