I recently played a duel, and my opponent was a Necromancer. Naturally, on his first turn, he made his Stalkers invisible. I had completely forgotten about them, and because of the poor spells in his spellbook, I placed a Crystal of Secrecy next to my Assassins, and it turned out that the crystal was placed next to the Stalkers, and they became visible :eek:

Anyway, building on the idea from Media about using Trappers to find Stalkers, I propose my improved method for revealing invisible units: D. Of course, you can't place the crystal where the Stalkers are standing, so we calculate that location and simply place the crystal next to them, and their invisibility is foiled. Another very good method is to place a Wall of Fire directly in front of the Stalkers (if they haven't made their second move); then they won't have much of a choice: either go straight through the wall and reveal themselves, or try to go around it, losing turns, which is not always possible, as their own troops may get in the way. By the way, you can expose hit-and-run units in the same way, and it seems that any hero can learn the Crystal of Secrecy (i.e., it's a spell below level 3).

Shadar, Divine Retribution actually depends on magic; I posted the formulas on the first page, you can take a look and see for yourself.