Won't you explain? I just can't seem to get the hang of this spell...
(At the beginning, it seems ineffective and consumes a lot of mana, but by the end, other, more powerful spells appear.)

This spell looks incredibly powerful on the Sorceress. (As do all schools of magic, the question is just finding the right spells). This is already beyond balance; it's outright cheating. Let me explain: with alt-druids, you have a plethora of spells, and with the help of Rain, you can set up 3-4 minefields. Imagine what will happen to the enemy's troops if they start running through these fields. =)
Also, I really like the spell "Vampirism," even though it ruins the reputation of vampires in the game.