Fire Energy CLL FIR is a core Energy card used for Fire-type Pokmon strategies
Osgir represents a trend in Commander, which is Wizards reaching out to people like Sheldon Menery for help designing Boros cards that dont suck
Combined with a number of strong anthem effects (Benalish Marshal, Deathbringer Liege, Glen Elendra, Thistledown Liege, Valiant Knight, etc) the deck can very quickly overwhelm and dominate your opponents
Card Kingdom
The dream is playing this on turn 2 as a Rampant Growth effect, and that will come up occasionally, but as the Nurturing Pixie decks have shown us, just being able to bounce a creature back to your hand to reset an Enters ability can be good enough
Dragons hit hard, fly over blockers, and have deep tribal support, though they need a strong ramp base to perform