Insane idea but could blind the bear and Lure away from the path with sound with the cannons or something else like the mages using extremely loud spells while the rest of the army runs through the path while it's distracted with the loud sounds and smell of gunpowder .
We think alike.
Guys can I get you interested in this plan that doesn't relay in trying to back away artillery or managing to calm an angered super-predator?
[X] Plan: "Actually, you see shit."
-[X] If possible, stick sensory deprivation illusions or other hazards upon the Ursa Major. The intention is to confuse its senses or outright blanket them. It doesn't matter if it realizes that the world outside isn't actually a black void, if it still continues to see the world as that black void, with cacophony of noise coming from all directions and completely contradictory smells to further make a mess of its directional sense and detection. Or if its eyes are covered by suddenly appearing tarps or sticky (and maybe burning) tar. This, in effect, should allow our troops better chances to combat the giant.
-[X]If the latter isn't possible, then Merlin and subsequent mages are to try to slow the movements of the bear, like breaking the ground under its feet, or to lob fireballs and other such spells at it to bring damage.
-[X] Our knights are needed at the front, with some of our normal ranged troops to act as additional bulk and diversions. Their goal is to keep the beast away from our artillery and to attack the bear from all sides with their weapons that should damage the clearly magical beast.
--[X] If the ponies think Pegasi's thunder attacks can work on a Ursa Major, add them to the attackers.
-[X]Artillery will reorient and start firing upon the beast, with flamethrowers acting as a hopeful deterrent for the bear in case it gets close. If effective, they shall continue firing, hopefully aiming upon center mass of the giant without hitting our own troops. If artillery seems ineffective, they shall retreat, allowing greater surround by the knights.