The most outstanding card is created by Atsuko Nishida, the original creator of Pikachu's character design
While there are more ways to add counters to creatures in Avatar: The Last Airbender, compared to most other sets, Heartless Act can also remove counters from creatures, which gives it a lot of added versatility
White is secondary in this ability, which means it tends to do it more often at uncommon and usually at a lower power level than green
Its popped up in Legacy a bit recently due to its synergy with Ancient Cellarspawn, but not in huge numbers
Even without going that extreme, all three teams that finished in the Top 8 of the Team Constructed Open that played Urza, Lord High Artificer played a full playset of Emry, Lurker of the Loch, which represents impressive adoption and success rates
How can I avoid returning the dashed card to my hand