when you use this brutal heart:
When you use a Subterfuge Skill, leave behind an unstable Shadow Decoy Trap that Taunts enemies. The shadow Decoy Trap will explode after 5.5 seconds dealing X shadow damage. Cannot occur more than once every 5 seconds.
your decoy will sometimes end up in blind effects on the ground from various mobs and the nightmare dungeon affix ‘drifting shade’.
When the decoy is inside the effect (drifting shade, tornadoes from tomb lord, fire blind from bandits, etc) your entire screen will be black as if you are standing in the effect yourself. This makes it almost impossible to reliably do drifting shade NM dungeons while using this heart. Im unsure if this also applies to the regular Shadow Clone ability and unique gloves, but it might.