A vertical cycle is a cycle that encompasses different rarities, usually from the same color , so you have a common, an uncommon, and a rare that do similar stuff
Its ability to ping all opponents whenever something dies, mills, or leaves the graveyard creates a constant stream of chip damage
Unfortunately, it quickly became apparent that building a deck around Vivi resulted in a playstyle that just wasn't much fun, and the card's value quickly normalized
Since you have access to blue, you get all sorts of control elements between counterspells, extra turn effects, and bonus card draw
Mewtwo (Great Rocket's Mewtwo) and a Lugia holo, again, with beautiful illustrations, the classic WOTC star holographics, and a high rarity, which many wanted