Backtracking: I realized that this is an action story, which naturally required there to be giant eels. I mean, really. Why put your heroes in a sewer and not give them giant eels to fight? The trick is to have the giant eels mean something.
There were giant eels. Which was a bit of a surprise, and also wasn’t. This wasn’t really the sort of place for giant eels, but there was always going to be something. Still, there just weren’t as many giant eels as the party might have reasonably expected.
The first two giant eels revealed themselves through the time-honored tradition of suddenly rearing out of a submerged cistern, grabbing Anton, then swiftly dragging him underwater before the other four could react. Immediately, Maddie snapped out a spell that wreathed her form with buzzing, oily bubbles of energy, while Jack and Jill leaped up from the walkway to find whatever handholds on the tunnel walls were available. Susan looked around, curiously. “That’s odd,” she said as a blue-grey glow surrounded her. “Giant eels usually hunt in packs of six or more.”
Two more eels leaped from the waters to fall upon Susan — only to bounce off of the glow. “Ah,” the priest said. “There they are. Still not enough of them, though.”
Maddie strode forward, her hand coming down on one eel’s stunned form. The oily bubbles flowed down her arm and onto the eel; it shuddered and died. “I apologize,” she said, then turned her attention to Susan. “Maybe they’re lying in wait?”
Jack and Jill were leaping down now, their claws fully extended and poised to strike perfectly at the eels’ vital points. It died as quickly as the other one. “This one smells like it was injured,” said Jill as Jack started carving off choice pieces of still-warm flesh for much later. “Maybe they were in a fight?”
About then, the water around them suddenly swirled dark. A few moments later, Anton surfaced, his face dripping eel blood and his hands full of chunks of flesh. “Saved you some, honey,” he said. “But where’s the rest of them? Giant eels usually hunt in packs of six or more.”
“I was just asking that, dear,” said Susan. “And they usually don’t like sewers.”
“Well, sure,” said Anton. “Humans live in ‘em, after all. These must have been desperate.”
“Or hiding from something that scares them more than humans do,” said Maddie. “Which is good news for our mission, I guess.”
“Kinda,” said Jack. “Definitely kinda.”