This deck is a lot of fun to play. 8 creatures have the effect "Gain 1 life whenever a creature comes into play." Genesis Chamber works to keep even more creatures coming onto the battlefield, triggering more lifegain. Nyx-Fleece Ram provides some defense and more lifegain.
Eight cards, 4 Ajani's Pridemate and 4 Archangel of Thune, harness all that lifegain into +1/+1 counters.
Pridemates are cheap and will be big targets for opponents when played early. If they aren't removed they will grow and win quickly.
Archangels come into play later. When you play an Archangel of Thune onto a board that provides life when you play creatures, your creatures, all of them, grow. Multiple creatures mean more lifegain mean more creatures getting all the bigger. Genesis Chamber triggers another wave of lifegain-triggers and creature growth, all in response to the Archangel being played.
This deck has a lot of small cards that don't seem that threatening, meaning the opponent may leave them in play. Opponents are forced to use removal on the Rams and on Ajani's Pridemate. When you finally get that fifth mana and plop an Archangel, it is usually too late for the opponent.
Brave the Elements and Launch the Fleet add surprise and versatility. Brave the Elements can protect white creatures or make them difficult to block. Launch the Fleet can add yet more creatures, hopefully causing more lifegain and triggering an Ajani's Pridemate or Archangel of Thune for each lifegain triggered for each token created.
The sideboard provides some responsiveness, while keeping with the creatures-coming-into-play-trigger-lifegain-and-explosive-creature-growth theme.
