Shimmer Myr has no effect on artifact lands because they aren't cast as spells
Costing two generic and two black mana for a 4/3 snake glimmer enchantment creature, Enduring Tenacity has some board presence, but for the most part it's considered purely for its triggered ability: whenever you gain life, target opponent loses that much life
This goes to show how format defining free reactive cards can be, and as long as Fury is regularly played in the format, I doubt that any strategy relying on going wide with creatures will be a good choice or even a Tier 1 deck
There's going to be a ton of previews, so stay tuned as those all come out
What makes this so good is that you only need a dork of a power four or more to work, so every Commander with it should toss this in, as welk as in ones that pump your Commander's power like auras, equipment or Voltron
Number 3 Both of these are quite powerful