Six-limbed stealth slayers are frightning creatures to behold. They prefer to keep to themselves, cloaked by their necrvisual powers. But if disturbed, slayers emerge from their invisibility, physically attacking any creature they perceive as threatening.
Stealth Slayers are probably one of the sneakiest enemies in the game. There is no way to tell if they will appear unless they attack you, but one Hero can tell where these Darkspore are hiding. Slayers aren't very dangerous unless accompanied by other Darkspore or other slayers.
Goliath's passive ability, Targeting Reticle, will tell you when a slayer is about to appear, because you will see the target reticle over an empty space. This signals an enemy is being targeted and then the stealth slayer will appear.
Another way to notice them is if you walk and somthing quickly moves past you, but blocks you. This is a stealth slayer still in hiding and attacks like Sage's Strangling Briars will probably reveal a group of slayers, this is a great advantage because slayers can't go back into stealth like Pterodynes.