After you defeat the Lingering Torment, pay attention to the environment. Notice that a dream/memory of Graucus is there, and he was the one fighting the Lingering Torment the whole time (along with his allies). If you go into the building behind him, you'll notice a little girl cowering in fear. And alongside her, a little duck named Peppers.
We know that this was a victorious battle, but he could not shake the terror of that day.
From all this, we can gather that Graucus had - at some point - nearly given his life for a perilous battle to protect a little girl, and her pet duck named Peppers. Given how difficult that battle was with us (and it was just a memory), one can only imagine how much more perilous the real thing was like.
No wonder Peppers sought him out in the Dream when he (presumably) passed later.