Back on the track of player messages to find that shortcut, I come across a long bridge across the lava guarded by another stone lightning thing which thankfully I could just run by since my gear was pretty broken at this point. Non hostile parasite bugs crawled away as I made my way down the large corridor only to find Solaire waiting for me. A particularly bright bug had attached itself to his head, and he now believed himself to be the sun - demanding praise.
I tried to reason with him, but to no avail. He drew his sword and attacked! Fortunately I knew all his moves after seeing him in action so many times. The battle also served as another parry and riposte test since I was in no condition for a drawn out combat. I killed Solaire, and a little bit of me died with him. Judging from the player messages left nearby, I wasn't alone in that feeling.
Good bye, old friend.
The giant door behind him led was indeed a shortcut to the bonfire, which skipped the long trek through lava and dragon dinos and made the melting ruins easier to explore (it was easy enough to sprint past the bridge keeper). After slaying a witch, I found the boss of the area: a great tree who technically only has 3 hit points: I just needed to hit each weak spot once to win. This was by no means easy though, as the floor would give way to insta-death drops and her sweeping branches enjoyed pushing me into said holes.
This is why I hate trees!
It took a few tries but finally I got into the core of the tree where its true form, that of a helpless insect was revealed. I took great pleasure in squishing that bug to claim my second lord soul and warping out of there.