This card first appeared in the Mirrodin block (one of the first modern-frame blocks) and this classy time-shifted version is worth $7
The only reprint worth over $10 is Door of Destinies, and Id say its safe to assume that original cards may lose a bit of their value with time
Every time you swing with Birds with Choco out, you get to dig into your deck, draw a card, and drop (potentially) multiple lands into play at once
The other option is defaulting it to being exiled, which is a nice recursion to get more value, but kind of expensive
While Mindwrack Demon is impressive as an early threat, the flexibility offered by Traverse the Ulvenwald in long games seems like it may end up ultimately being the real payoff for the mechanic
A mana rock refers to any artifact that generates mana