In addition to making a giant number of Rats, Marrow-Gnawer gives them all fear, meaning only black and artifact creatures can actually block them
If you have some Standard staples that will be rotating soon, you should try and trade them before rotation: Their prices will usually drop post-rotation
Basically, the TLDR is that you can build an almost infinite number of really fun, solid, and competitive Commander decks for free with the help of the card-rental programs
While gaining and draining have long been staples of the Aristocrats archetype, this decklist feels like a better marriage of those two themes
Creature - Shaman Snake Color tag templates(None) Solemn Simulacrum When this creature enters, you may search your library for a basic land card, put that card onto the battlefield tapped, then shuffle