In second fifth place, also with over 2,400 decks on EDHREC is Marwyn, the Nurturer
Budget Xenagos ($50) Upgrades and Fiddly Bits I love cheating creatures into play, so the first cards I'd recommend adding to the deck do just that: Elvish Piper, Quicksilver Amulet, and Sneak Attack are wonderful
Restricting yourself to a single spell the turn you cast it is often better than casting nothing
Organization Systems Alphabetical Order Alphabetically sorting your cards is one of the simplest and most intuitive methods
In Monoblack, for Commander, the super accessible lifegain effects focus around death, and not entering, and that means Moseo might be a tad slow
Its worth taking a moment to evaluate each of these cards on their own merit here before we plunge into how you might upgrade the deck