even if he is specialized in killing, killing alone doesn't guarantee his well-being. He is an artisan of WAR. War can be a large, brutal melee of both sides constantly clashing. If his specialty is killing and fighting in the front lines, what better way to preserve such skill and ability to keep fighting than having him use a shield with such incredible defensive capabilities. A spear is already a tool for killing that he is quite adept at, he just has to point it in the right direction and spears can be replaced, but a shield that can technically block even tower shots, which technically even Braum's true-ice imbued door-shield can't do, is amazing all on its own and will help keep the artisan of war alive to shield-slap some poor unfortunate bastard another day.
Also the downvotes probably come from the title which is questioning the fact that he even has a shield when he is thematically modeled after the image of Spartans (Getting kicked into a well is the least of your worries) , with his armor resembling those times (I'm no history expert but the armor of around those times, commonly seen in old Rome-themed movies as well) Where a shield, usually a large one, was a very commonplace thing to use alongside a spear because you could hide behind it while jabbing at attackers with the spear's long reach. Sure it sounds kinda meh, but in those times, you did whatever you had to do to win and stay alive, no matter how underhanded or cheap you might think.
