Why the card was graded at Mint 9 and not a Gem Mint 10 - the highest possible - remains an open question
I know I said that this is more of a competitively slanted card, but it actually has some decent chops in EDH as well at around 1000 decks its a big player in both mill decks and Rogue decks (and mixtures of the two), of course being very popular with Anowon, the Ruin Thief
Balthor the Defiled, Karador, Ghost Chieftain, and Chainer, Nightmare Adept are the best commanders that fit into these decks
It's similar to if you granted all your Knights lifelink, but cooler
Cavern of Souls also fixes colors for typal decks, meaning archetypes like Azorius Spirits in Pioneer can easily cast both Mausoleum Wanderer and Skyclave Apparition when necessary
Now I'd like to share some of my playtest card names, which are basically the names that a card designer (like me!) will use to convey something about the card