I started a new character the other day and cruised my way through the early game until I made it to the Depths. I wanted to level my pyromancy flame up, so I stuck my summon sign next to the bonfire to help people take on the Gaping Dragon and nab some souls.
The first summon was very nearly a shitshow, as the guy hadn't killed that Channeler up above the fight area that buffs the dragon's attack (almost 1 hit kills with the weakest of attacks) and launches spells at you. However, we persevered.
The second fight went smoother, up until the very end, when I died right before the boss did. Still, it gave me the humanity and souls before I disappeared, so if you're quick you can still make out nicely (which is nice to know).
Things fell apart around the third. I always stick close to the host and follow them wherever they go. I figure it's a matter of courtesy, it's their world and I'm just here to help. The host didn't immediately beeline to the boss, so we went around stabbing things and they collected the loot. All well and good up until the point where I rolled wrong and fell down a hole straight to the area filled with cockatrices.
After a madcap dash out, narrowly escaping being cursed several times, I went about trying to find my host. I know the area fairly well, I've got multiple playthroughs to my name, so I figured it would be fine. Well, after retracing my steps I couldn't for the life of me find the guy, up until the NPC Kirk invaded. I dashed down to where it happens, despite having circled my way around to the complete opposite end. By this point Kirk had been defeated, and when I arrived my host was nowhere to be found. Right then, the host summoned Solaire, which is right next to the gate to the boss. I sprinted all the way there and arrived just in time to fight the dragon. We fought it and emerged victorious.
Moral of the story: keep an eye on your summons. You never know what kind of hijinks they might get into if you don't keep them in your sight.