Your merc is the most important minion of your army, he must have the best weapon. Infy is the best. Pride is shit.
Infinity has high damage, that makes your merc killing enemies faster.
40% crushing blow to kill bosses faster.
Conviction aura lower enemy resistances 85%, making your corpse explosion do a lot more damage as it is 50% fire damage.
Convicyion aura lowers enemy def by 83%, making you army hit a lot more.

thank you . was a big help