Magick Cannon and Great Cannon are versatile spells that can be used to quickly dispatch powerful foes if used correctly, but there are certain limitations on what it can do.
Multiple cannon spheres can be summoned at one time to increase the number of shots fired, and can be elementally charged. Summoning and firing two spheres in conjunction with each other is the most efficient means of using this to the player's advantage. One sphere often does too little damage, and by the time a third or fourth sphere is placed on the field, the first sphere is likely about to fade. This tactic can turn the Mystic Knight into the medieval equivalent of a heavy machine gun emplacement.
The type of strike the sphere receive seems to impact the damage each individual shot does. For instance, a normal sword/mace strke can do a fair amount of damage, while a strike from an attack that hits an opponent (or sphere) multiple times, such as Antler Toss or Full-Moon Slash will generate a huge number of projectiles with very little actual power behind them.
The Cannon can also be combined with Perilous and Ruinous Sigil. When an enemy strikes the sigil, it will trigger the cannon to fire in that direction and deal additional damage. Similarly, a Stone Forest or Stone Grove cast next to the sigil will fire off a number of projectiles, though the charge time and stamina cost makes other options more efficient.
Enemies, particularly large enemies, can trigger the sphere when they strike it, occasionally hurting themselves in the process. Pawns can also fire the Cannon by striking it.
Key to getting the most out of your Magick Cannon is to enchant your weapon beforehand using one of the Mystic Knight's various elemental weapon enchantments. This will impart the elemental property to the Cannon, making it deal more damage, and taking advantage of the elemental property in question (extra damage to undead from fire, for example).
Magick Cannon persists for 12 seconds and Great Cannon persists for 18 seconds.
use with holy enchantment for long range damage plus healing.
If you have a Sorcerer, a Magick Cannon can be placed inside the (High) Maelstrom spell, as they will permanently trigger it until one of them fades.
Great Cannon uses 40/60 split of str/mag to calculate damage.