Go into DS Academy and ride the Drake there. It'll take you to a place and you go inside an instance. Malistaire is really tough. He has 3 Undead Wizards with him and his health himself is 10,000. Even though I am only lvl 31, I know this because my lvl 50 friend took me there and helped me fight him. Good luck! :D
Scarlet HawkHeart Magus Sorcerer (Lvl 31 Balance)
P.S. BE SURE YOU TAKE AT LEAST 2 FRIENDS WITH YOU, FOR IT IS IMPOSSIBLE TO GET TO MALISTAIRE WHEN YOU'RE WORKING WITH YOURSELF. There are puzzles all over the place that 1 person has to do, and 2 or more people have to kill monsters while the person is working. Malistaire's Lair is not just a room with Malistaire himself waiting; it is a big chamber with puzzles, traps & monsters everywhere. It's an instance so you can bring 3 friends along.
P.S.S. I recommend you bring 3 friends, the maximum, because it makes it easier to defeat Malistaire with, he has 10,000 health, not to mention 3 monsters along with him fighting. I would also make all your potions full. ALSO, if you get in a fight with a roaming monster, don't flee, press ESC, quit, and log back in, then port to a friend. This saves trouble as your mana doesn't get wasted.
Malistare is easy to find i defeated him 2 times all ready!!! hes is in the great spyres first defeat 2 onis and the door will be unlocked go pass his door now defeat 2 of his dragon guards after that go pass the door and go to 4 more of his guards and after you did that talk to malistare and defeat him defeat because he trys to try to destory wizard city with his wife and he kid naps the myth school techer!!!!!!!!!