In each color, theres a card that says if you control a commander, you may cast this spell without paying its mana cost. As you might imagine, theyre all kind of bonkers
You also get useful staples and easy upgrades in the same shell, so it teaches core Commander fundamentals while still feeling powerful out of the box
The abilities granted by backup are determined only when the ability goes on the stack, so losing abilities before the backup ability resolves won't change its effect
Yargle, Glutton of Urborg is a vanilla creature, but that 9 power encourages you to go the Voltron commander route with your best equipment and auras
The real kicker though, and its definitely a kicker, is that on top of that, it also deals two damage to you and each Creature you control whenever its tapped
That, coupled with the growing dominance of the deck, pushed the meta towards SM99 decks and decks that counter it, pushing out decks without game plans that directly circumvent [card]Spider-Man 2099[/card]s strengths. Thus, it was banned as commander in order to preserve competitive archetype diversity and freedom in deck construction. Lumra, Bellow of the Woods Lumra, Bellow of the Woods received a ban for similar reasons