This deck has Kalonian Hydra and Solidarity of Heroes to double +1/+1 counters.  Heroes' Bane essentially doubles its own counters, too.

Setessan Tactics is an attempt at creature removal.  This is a creature-heavy deck with a lot of mana, and not many free card slots, so I chose Consign to Dust for artifact/enchantment removal because it can have many targets.

There's not much protection in this deck.  I'm relying on the abilities of Scourge of Skola Vale and Vastwood Hydra to keep +1/+1 counters on the battlefield even when creatures die. 

Bassara Tower Archer can be played early and provides devotion for Nykthos.  It's not much good on its own, although it is usefully hexproof and has reach.  But Ordeal of Nylea can give it +1/+1 counters that can be doubled, helping it fit within the theme of the deck.  The death of Vastwood Hydra can also put +1/+1 counters on the archer.

I would have loved to include Aspect of Hydra in this deck but haven't found room for it.  It could temporarily increase the toughness of a creature who is about to be sacrificed to Scourge of Skola Vale, or to temporarily increase the power of Heroes' Bane right before using its activated ability.  Plus it would be handy for beefing up a wimpy creature if I haven't gotten to play any big ones yet.

The theory behind using Elvish Mystic and Sylvan Caryatid, along with a slightly low number of basic lands, is that I need to ramp up my mana fairly quickly in the beginning of the game so that I can play key cards like Kalonian Hydra.  After that, though, I might end up with surplus mana.  Elvish Mystic and Sylvan Caryatid can help me add mana quickly, and then later in the game they can be sacrificed to Scourge of Skola Vale if needed.  Plus, Sylvan Caryatid is hexproof, so even though it has Defender it could be a good sink for +1/+1 counters from Vastwood Hydra if I get desperate.  I could use Setessan Tactics to let it fight another creature.