The card draw with Kumena's Awakening and Secrets of the Golden City are decent
Captain America, Team Leader is appropriately red, white, and blue and gives other Heroes you control vigilance and haste until the end of turn when they enter play along with a +1/+1 counter, with Cap also getting a +1/+1 counter of his own
At any time you hold priority, you can turn it face up and activate its affects
Ive got your answers right here
With my Seraph Sanctuary and Bishop of Wings in play, giving me a boost of 50 life, my opponents had to have an exile or bounce wrath or face death if I untapped with my army
Paying four life seems a bit high for a single card, but the Library allowed you to effectively see into your future by a full two turns