Look at the monster, determine weak point, then throw spear at weak point while expecting I'll miss, Dual wield axe and sword if they are both one handed weapons then proceed to brutally dissect monster
if the sword or axe was a huge broad kind take sword and go berserk at monsters ass
I take the box and three weapons and find a fourth long skinny object somewhere then I affix all four to the box. As the monster is a lion it lacks the proper capacity to know how to deal with four targets at once (I forget the exact reason for this). I then proceed to tame the lion. I then proceed to ride the lion into battle wielding my three legendary weapons (why else would a box with weapons in it be guarded by a lion?) and a stick (or whatever) and conquer my enemies' nations singlehandedly. I proceed to rule the dominions I have claimed with an iron fist until the lawful stupid hero slays me. Unfortunately he did not realize I was a lich and failed to destroy my phylactery (the box) so in a few years time I return to bring horror to the world in the sequel.
You have a big scary monster, three weapon, and you are a hentai maniac. If there's an opening, why do you plan to attack the monster instead of running away?