What makes Vishgraz a good infector is that it makes three infect tokens, so those get in eventually and increase the poison all around
Naturia Beast Modern Yu-Gi-Oh is all about negates if you can go first in a duel, youll want to set up a bunch of negates to make it as hard as possible for your opponent to play
There's also a chance this card sees older format play, because even with its expensive cost, its Price of Progress-esque ability and big body might ask awkward questions of control decks that they aren't prepared to answer properly
Either way, two mana is a great rate for an effect like this and, with the Menace keyword, Dusk Legion Sergeant also threatens to get some damage over the line before it inevitably gets dealt with
Since its nearly uncounterable and costs less if you control legendary creatures, it fits perfectly into green-based midrange and ramp decks