This means the more rares/mythics you have from a single set, the more likely you are to get one you dont have when you open a pack
Keep him on the board long enough, and Vivi becomes a powerful attacker in his own right, but his real value lies in the win conditions you can create with the killer combination of free mana and pinging
That might be for cards that care about your opponents losing life, like Rakdos, Lord of Riots, or for lifegain payoffs like Drogskol Reaver
Luckily, this combo has far more stringent requirements for inclusion than Saheeli Rai/ Felidar Guardian
Thus, if you activate the ultimate ability of Tamiyo, the Moon Sage with 8 loyalty counters, Tamiyo will hit the graveyard before the emblem is created, and you will not be able to return Tamiyo to your hand