Unless they’ve been nerfed in chapter 3, the summoned demon is quite powerful. It starts off seemingly anemic, but quickly grows in power as you use it as it levels with each kill, no matter what you’re killing. It also gets some pretty hefty armor and strength bonuses, I mean the screenshot shows 270% extra damage.

Its timer also resets everytime it kills something. So if you need to farm kill a few things, the demon is actually quite good for that. And due to its temporary nature, its expendable at that. Its to be used as an expendable minion, not an enduring comrade. As it does want to kill you.