"Resistance will avail you nothing! I lay claim to all that I see!"
—Dormammu's victory quote.
Dormammu has a very versatile arsenal of projectiles; being the MvC3 equivalent of Blackheart. He can combine his two Empower Spells (Power of the Creator and Power of the Destructor) to make different specials which have different properties (multi-hit, OTG, wall-bounce, etc). He lacks mobility and is a large character, which makes him an easy target to rushdown characters. This is compensated with his very defensive-oriented zoning game, limiting the opponents movement area.
Dormammu has often been compared to Dhalsim and Blackheart, as he's a keep-away and zone character that specializes in controlling space. He has many ways to limit his opponent's options and keep them in certain areas while powering up his own attacks. Dormammu has an 8-way air dash and a teleport move which can help him escape some bad situations and his moveset offers players several different options. Some of his moves will leave gaps which your enemy can slip through, but when coupled with well-timed assists he can be very difficult to consistently get in on. When your opponent gets inside, though, they can take quick advantage of Dormammu's large hitbox and lack of up-close moves to get out of bad situations. If you cannot keep your enemies at a distance, Dormammu can be killed very quickly.