In match Id 29148742, 9:25 in game (13:10 on the replay counter) Myrmidon uses his wave form to charge through the behemoth fissure.
As long as myrmidon don't have vison of the fissure it can be done, even if only a small part of the fissure is in fog, he will charge through.
Is it intended to work this way?
Well at least someone finally found a bug that remotely surprised me in a long time.
I'm guessing this bug appeared since the fix was made so units pretended that things "weren't there" when they move into fog and a unit actually was there. So I'm not sure if this fix would be feasible to undo the super-important "pathfinding in fog" bugfix.
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Look for my highlighted text (important information) and grey text (interesting but not required information).
As you might expected, you can do the exact same thing with the dark lady, as her charging strike is similar to myrmidons wave form.