How to detect invisible enemies or npc?

[FB_Destroyer_Rebecca]

Hey, I am still early in the game but for god sake I cant remember how to detect secret enemies (rouges) or npc's. I know I could use a aoe-grenade or a aoe-skill but thats kinda the raw version of doing it. You guys know what I mean?

[kcnik]

In general you want something that has a huge AoE and can effect an enemy even if he has armor on. The best solution for that is Rain (at least fro what i've seen)