Hmmm. . . very strange. It could be a large level, and the fith enemy is just really far off.
-DarthMimic-
Either way, that level is zoomed out pretty far.
The only time I've seen anything like this is when the Necromancer Mini-boss in Unleashed PD summons his undead zombies and skeletons, and those always show up eventually (After saving the game).
When a new enemy spawns, a Potion of Mind Vision doesn't show the enemy on the turn it spawns. It typically takes a turn or 2 before you are able to see the enemy.
@ Ultimatecub:
In addition to what SuperSaiyan99 stated, there are times when an enemy isn't instantly revealed upon gaining the Mind Vision buff because the enemy in question was already wandering when the action of gaining Mind Vision took place, so they appear on the next turn instead, when the buff has a chance to catch up.
Your 5th enemy could very likely be around the corner, either in the "fog-of-war"/unexplored tile in the hallway above, or (more likely) the zig-zag/thunderbolt hallway below & to the right, where it's barely visible (which is usually the sign of an enemy in motion).
Good point. I've experienced that myself, Shadow.
@ Ultimatecub:
Also, if you don't move while you have the Mind Vision buff, it doesn't keep track of where the enemies go. Once you move again, it'll reveal their locations as long as you still have the Mind Vision buff.
True again. The Mind Vision lags on high-speed enemies, like the sewer crabs.