Its tough comparing Squire to Plea for Power, but recursion in a deck is something I believe to be more dangerous than anything else in the right scenario
Each transforming double-faced card in this set is cast face up
What's interesting here is that it's a state-based action - when you cast the spell or when the creature enters, if you've already gained life this turn you get a benefit
But blue players are spoiled with access to Mana Drain, Counterspell, Arcane Denial, and much more
Needing to pay two mana is significant, so if you can play the Eternal Soldier alongside Duke Ulder Ravengard, Soulbright Flamekin, or Aurelia, Exemplar of Justice you can do some tricky things
Hes really good at holding equipment such as Sword of Hearth and Home or Umezawas Jitte to get extra triggers when he deals damage, but you can also use him to tutor up Skullclamp in your tokens deck and then immediately equip it to him to draw four cards when he dies