Since the phrase is "mystifies X", rather than "mystifies target/each X", that means that the mechanic should be type-neutral to accommodate a wide variety of types.
...mystifies Shrines. (Shrines you control phase out. They phase in at the beginning of the next upkeep.)
...mystifies Shrines. (Exile each Shrine you control face-down. You may look at and switch them with a nontoken land you control any time you may cast a sorcery.)
The other, more kosher option is probably hexproof/indestructible until EOT like Tahazzar described.
Is it fight? That post is from 2010 and fight was introduced 2011 or so. Seems kind of strange to post it if it's fight but I mean, cool?
Another I could see is one-sided fight, but that's fairly recent design direction and IMO a (grizzly) bear that hits for 2 damage would not feel like at all.
Yeah, about that... Can you access the "Cardlist" or "Visual Spoiler" pages? This amount of cards in a single set unfortunately makes them impossible to view freely since that memory usage issue hasn't been resolved.
Since the phrase is "mystifies X", rather than "mystifies target/each X", that means that the mechanic should be type-neutral to accommodate a wide variety of types.
...mystifies Shrines. (Shrines you control phase out. They phase in at the beginning of the next upkeep.)
...mystifies Shrines. (Exile each Shrine you control face-down. You may look at and switch them with a nontoken land you control any time you may cast a sorcery.)
The other, more kosher option is probably hexproof/indestructible until EOT like Tahazzar described.
My first thought was:
...unsettles each opponent. (That opponent can't cast instant or sorcery spells this turn.)
...but it's a little too
to be a 
mechanic. So the other idea is:
...unsettles each opponent. (They can't target creatures attacking them with spells or abilities this turn.)
It's a bit of a bend, but it'd be found in
and maybe 
, as a "you're so nervous you can't aim straight" type of deal.
For a joke mechanic:
...unsettles each opponent. (Each opponent shuffles his or her hand, searches his or her graveyard, then says "Resolves.")
Since this affects spells on the stack, how about:
All spells ignite. (Ignited spells deal damage equal to their converted mana cost to their controller as they resolve.)
or
All spells ignite. (Ignited spells add one mana of any color to its controller's mana pool as they resolve.)
Both seem fairly niche, though.
Way too obscure. Things that pop to mind are rituals, cascade, replicate/fork, etc...
A completely mystefy to me. It could be anything, Grants hexproof and/or indestructible UEOT? No, that can't be it.
Discard would be my first instinct but that can't be it since it would be ill-advised for a mechanic (too much CA) and this is a common.
Maybe "exiles the top (X?) card(s) of their library"?
Others I could see would be somehow stop or make attacking or blocking harder. That doesn't seem particularly
though...
Is it fight? That post is from 2010 and fight was introduced 2011 or so. Seems kind of strange to post it if it's fight but I mean, cool?
Another I could see is one-sided fight, but that's fairly recent design direction and IMO a (grizzly) bear that hits for 2 damage would not feel like
at all.
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@rancored_elf
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Alternate idea for bifurcate: "\1, Exile this permanent: Create two tokens that are copies of this permanent."
Alternative name: Clone?
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Alternate idea for bifurcate: "\1, Exile this permanent: Create two tokens that are copies of this permanent."
Indeed. It is. Well, mine is uncommon. :)
Interesting. I use my own software to export the stuff and look at it as a MSE file if I want an overview.
For samples I usually just create a booster or use the search function and just check for e. g. white creatures.
I know the Visual Spoiler used to work fine not too long ago. Maybe around 700 cards...?
Isn't it furtonate now that I didn't additionally spam Cards With No Home?
Yeah, about that... Can you access the "Cardlist" or "Visual Spoiler" pages? This amount of cards in a single set unfortunately makes them impossible to view freely since that memory usage issue hasn't been resolved.
Hmm, I think Summary Dismissal is the answer to that (as well).