1 drop

Thoughtseize - Early creature into the GY most likely. I'd use Despise, but I'm worried about drawing it late game and probably need to target removal and counters late.

2 drop

Dragon's Eye Savants - Wall for Kin-Tree/Phenax. Doesn't have defender, in case I have to put Nighthowler or something on it.

Kin-Tree Invocation - Turn a wall into a fat guy.

Negate - Protect my creatures.

3 drop

Wall of Frost - Devotion for Thassa, toughness for Kin-Tree.

Guardians of Meletis - Colorless will make this easier to cast than Wall of Frost .

Hero's Downfall - Kill.

Nighthowler - Can get fat off the mill, which also helps Kin-Tree.

Sultai Charm - Removal & Draw

Thassa, God of the Sea - Possibility of activation. Unblockable Kin-Tree could end the game early.

5 drop

Phenax, God of Deception - Mill the fatties.

Prophet of Kruphix - Double the Phenax, double the fun. Plus, you could cast her, then flash in Phenax on the opponent's turn if you've got both in hand. Speeds up the end-game, is what I'm saying.