They'll have Magic: The Gathering Foundations cards from a suite of Foundations products to support their deck building, and they'll be judged on their ingenuity within their deck theme requirements
SHRIEKMAW Shriekmaw is probably the elemental I encountered the most of when I first started playing Commander, and for many years basically until Ravenous Chupacabra hit the scene it reigned as one of the better options for an EtB removal spell low on the curve, that could be reanimated when needed
No more Bandlands, Bayou, Plateau, Savannah, Scrubland, Taiga, Tropical Island, Tundra, Underground Sea or Volcanic Island
Outlast is an activated ability that you can activate during your main phase to put a +1/+1 counter on the creature
A second good way a surprisingly good way is to go hard on five-color dragons right from the start
The Best MTG Commanders for Beginners Krenko, Mob Boss Few commanders feel as gleefully explosive as Krenko