Monastery Mentor proved itself to be one of the best finishers in older formats like Vintage, where it's easy to chain together cheap spells and cantrips to potentially make a lethal army of prowess tokens in just a single turn, which is certainly strong but still doesn't really feel broken to me
All standard-sized card sleeves will fit
Note that were specifically covering cards for the 99 in this article
There were some early sets that were enormous in size like Legends , but other than the erroneous Arabian Nights Mountain, basic lands and sealed-deck staples weren't an auto-include part of sets
As long as it has at least one time counter on it, it isn't a creature
On your first extra turn, do it again: cast Nexus of Fate for an extra turn, then tutor it back out of your library with Mystical Tutor