This deck is all about acceleration of mana base, landfall and card draw. Several cards outside of the commander allow for pulling lands from the library, and many cards take advantage of landfall mechanics or can sump large amounts of mana for great affects.
The sideboard are cards that were considered but were either too expensive to acquire or not already in inventory.
There are several themes to this deck, with no single combination that can get to a win. The first and biggest theme is accelerated land fetching from the library. With the ability to pull a land for each creature cast once Karematra hits the field, this deck can quickly grown lands. Add other land pull cards like Aniok Guide, Courser of Kruphix, Sylvan Primordial, etc, this deck can very quickly flood the field with mana sources.
The second theme of this deck are cards that take advantage of a land entering the battlefield, or better known as the Landfall mechanic. Since I'm pulling lands more frequently than normal, these cards allow me for some additional actions each turn, or in the case of creatures, an additional boost for the creature.
The third theme is creatures that, when cast, can get great benefit from all this available mana. Hydra creatures with X in the casting cost are my favorite, but other cards with multi-kicker, such as Joraga Warcaller, are great ways to use this extra mana.
Fourth theme is open-ended activated abilities. Cards like Helix Pinnacle, Soul of New Phyrexia, Elder of Laurals, etc. all allow for this extra land to be used how ever many times can be afforded. The point of this and the X cast/multi-kicker cards are to sump the extra mana for big creatures or big effects. The spells like Consign to Dust and Setessan tactics also sump the mana due to the Strive mechanic.
A fifth theme, on a small scale, is accelerated card draw. Cards like Explorer's Scope, Abundance, Nissa, Garruk, Ajani, etc., all allow for me to pull additional cards throughout the game. This rapidly, in combination with the land draw, thins the deck and gives me many more opportunities against y opponents.
Finally, the enchantment creature cards with the Bestow mechanic are available to use the higher mana. Early in the game when mana is limited, they can be cast as a creature at a lower cost, or once the mana flows, they can be cast as a enchantment on a creature at a much higher cost.