"erebus prema mist is so cheating, he must have a mod !! lmao"
That actually is not far from truth. I have tested it and even when u start ur mist with 7k mana it will be completly depleated but u will stay in mist for some reason. Erebus perma mist is a example of poor programing. Even when you have cloak of night, 500 helmet, 1500 helmet, 1750 helmet, 3300 helmt and 5500 helmet - The regen still wont offset mist 1 mana usage. Meaning u will eventually drop your mana to 0, but mist wont be stopped.
On cataract when you own mana flag u dont need 5500 helmet to stay in perma mist. Its great to spawn minons coz mist heals them.