Life(gain) is a Journey (EDH / Commander)

"Life[gain] is about the journey, not the destination."

• Unknown
  Well screw that, life gain is about pissing off your opponents with the ability to withstand anything they throw at you and just keep chugging. You can't reach the destination of pummeling your opponents with a butt-tonne of Pegasi if they kill you on the wonderful journey.

Let's start with the commander, our wonderful Atalya, Samite Master. We begin the defense with the ability to negate X damage to a creature or gain X life. You may ask yourself, why not just have "gain X life"? Well that's what we want our opponents to think. Little do they know, that their deathtouch is now useless. Their Walking Ballista? Nope. Your creatures are safe. It's so great, because the damage doesn't have to be all at once either. If X is 10, if can stop 5 from a combat, 3 from a Lightning Bolt, and 2 from a Shock.

What else do we got? Well, we're on the journey of lifegain, so of course, we have 14 cards that have the (nearly) sole purpose of supplying us with that sweet sweet life juice. Things like Celestial Mantle and Beacon of Immortality being the heavy hitters, and a bunch more for the incremental lifegain. The deck is also chalked full of lifelink, and other lifegain affects.
What's the point you may ask? Well remember the pegasi from before? Well BUBAM.... enter the Storm Herd. No? You don't enjoy using a d100 to represent how many pegasi tokens you have? Well then you'll enjoy our basic (and boring) Fellidar Sovereign and Test of Endurance.

But there is more than one way to die in a commander game? Ever hear of Commander Damage? Well, Atalya hasn't, and that's because we run over 11 cards that deal with just preventing damage all together. Sorry Aurelia the Warleader players. In comes Delaying Shield. This card is amazing. Not for it's life prevention ability (but that's okay too). No, what it is good for is the ability to stop any form of combat damage from happening to you. No Commander Damage. No Vraska the Unseen assassin damage. No Scroll Thief is going to draw off of you, and a slew of other combos are neutered because of this awesome card. And of course, the same goes for the various other protection cards we got going on.

Lastly, because many of our cards, Atalya included, have X in it's cost, we're running a total of 12 mana rocks, and other forms of ramp and fixing, including Weathered Wayfarer, Land Tax, and Endless Horizons.