The lifegain is to
balance up the life loses from painful truth. It is part of the main strategy but not the core. The core is still hitting delirium as fast as possible and then jammed out delirium payoff cards to close the game. I have considered running 5 pieces of lifegain solely, but this won't allow me to consistently hit my sweeper card dusk. Same goes with sweeper. Running 4 dusk seems too overplayed. 3 Painful Truth running together 2 pieces of lifegain (Aetherspehere Harvester, and Black Gearhulk) can almost guarantee to hit these 2 cards in 80% of the matches played. Therefore, a combination of 3 painful truth, 2 lifegain and 2 sweeper are more well balanced.
Prepare//Fight and Kalitas
serve as the 3rd and 4th lifegain against some really fast aggro and burn deck.
Black Gearhulk is preferred over Prepare//Fight because of the synergy with Traverse and Lili. Black Gearhulk is guaranteed to make a play when it goes into 8th turn. This also served as the boss card for this deck and replaces SovereignSky Ship or Ob Nixilis. Long time ago, this spot was always reserved for
Emrakul, The Promised End but she got banned. In
hour of devastation, will be looking at some possible cards for this spot.