This enchantment costs six total mana and won't affect the board once it resolves, but its effect is strong enough to make up for that in most players' eyes
It can be a mana rock, draw you cards and help you proliferate
Back in The Brothers War, for example, we got the bottom-left corner of Myrel, Shield of Argive
That makes it one of the most explosive mana dorks in Magic, though a $100+ price tag means you dont see it at tables too often
This commander wants nothing more than to fire off a Toxic Deluge before the commander
For three mana, Fraying Sanity is a Blue Curse that reads, At the beginning of each end step, enchanted player mills X cards, where X is the number of cards put into their graveyard from anywhere this turn. As above, thats great if youre in mill, but kind of rubbish otherwise