We knew these would go for a fat wad of cash, and sure enough they've proven their status as a collectible well worth slavering over
That's the joy for them: gaining knowledge, applying that knowledge against worthy opponents, adapting, gaining new insights, and evaluating how to change their behavior to do better next time
When you discard your hand, madness lets you put the Basking Rootwallas into exile instead of your graveyard, while the Vengevine waves at them as it goes directly to your yard
Like most Magic: The Gathering cards, the value of Archfiend of Despair depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Battlebond)
Now Wizards has made good on its hints that Vivi would be removed from Standard, but it's also banned a couple of other problematic cards alongside it
One buffs all of your other Demons, Devils, Imps, and Tieflings by +1/+1 and grants them lifelink, while the other summons a 1/1 Devil token each end step if a creature entered your graveyard that turn