That's a good kicker to have on your
mesmeic fiend, and a great ability for a mesmeric fiend to have.
Also for those wondering: the phyrexians and snow are indeed real:
This got leaked earlier and confirmed today:
Vorinclex, Monstrous Raider
4GG
Legendary Creature - Phyrexian Praetor
Trample, haste
If you would put one or more counters on a permanent or player, put twice that many of each of those kinds of counters on that permanent or player instead.
If an opponent would put one or more counters on a permanent or player, put half that many of each of those kinds of counters on that permanent or player instead, rounded down.
From the comments this stops your opponents sagas from advancing, and turbos yours (multiple chapters do trigger if you get multiple counters at once).
As well:
Doubling season specifies that the counters must result from an effect, while loyalty changes are a cost. In the fine print, costs are not considered "an effect". Vorinclex here has no such caveat.
When your opponent activates a +1, the counter doesn't appear.
When your Oko makes a food, that's a +4.