These cards do appear often
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The card includes 11 different Oracle rulings to go along with the words that are actually on the card, covering myriad potential questions about exile, cage counters, and what happens if multiple cards with the same ability are exiled with the aforementioned cage counters (Mairsil will have multiple instances of that ability
It's the kind of card that many collectors will have just forgotten about or assumed would be worthless, so if you have one, better get selling
This year the format was Platinum-on and your deck could only contain 30 cards, with no more than 2 of any card in it