For just six mana, Seshiro provides what is essentially a permanent Overrun for all of your other Snakes, and lets you draw a card whenever one gets through for damage
The rides
You know it, I know it, my editor knows it: its a one-mana token-doubler
A Platinum Angel that can be flashed in is quite cool, and in many decks having a Platinum Angel that isnt an artifact means it has a higher chance of staying around, as it wont die to Shatter effects on top of creature removal
Perhaps if they printed a way to also delete yourself as a targetable, vulnerable entity then you could just leave your opponent to slowly run out of cards to draw, trapped alone in a desolate waste
What's important to note about this layout isn't the exact positions of the general gameplay areas (graveyard on left or exile on right), but rather how I'm separating out the graveyard itself