Sure, it costs eight mana, but considering it has delve, which lets you exile cards from your graveyard to pay for its cost, if you could get seven cards in your graveyard, the reward is a sorcery-speed Ancestral Recall legal in formats like Standard and Modern
Dragon Shields are incredibly durableperhaps the most durable sleeve on the market
Kawaguchi interview (2000): "1" ("For the first year and a half, Tajiri-kun brought in prototypes, but then he stopped working on it.") Hatakeyama & Kubo (2000), p
But, the upside here is crazy, as getting a 3/3 + whatever your opponents best creature is will be a great deal for 5 mana
Sol Ring is so ubiquitous to the format that it's shown up in almost every Commander preconstructed deck ever released