1. Take a Mage w/ spellsteal into the Horde Mines near Frostwolf GY
2. Spellsteal "Fire shield" from one of the Rat Miners.
Fire Shield
Does 50 fire damage to any enemies within a 5 yard radius around the caster every 3 seconds for 15 sec
Here is where it gets good, its a 1 to 1 ratio with your +spell dmg, so Mages with 700 Spell damage will have this AoE hitting all targets every 3 seconds for 750 dmg, w/o any mana costs. (lasts 2 minutes)
Proof -

Tried this last night in AV with a Mage friend of mine, and he was only able to get it to stack once (says you can stack it more in the video). But he was owning people without even dismounting.
Lol, Thought I might also add. It will still effect your enemies even when your Ice Blocked.