As Lyra plunged her blades in the serpents remaining eye, it screamed as much as was posible underwater and violently thrashed around, the shots from the two remaining drones hitting it in random locations as the serpent moved too eratically to hit it in the same spot time and again.
In an unfortunate turn of events for the serpent, its trashing around made it so that Rita's last spear hit it right in the head, where it would have otherwise merely scraped past it had it remained still. With the spear percing its skull, the serpent was killed almost instantly. As the serpent's still-twitching body sank and eventually hit the bottom, it crushed some of the underwater houses the mermen built. But a few seconds after this, and as Chafla predicted, the serpent's body disolved, leaving a dark blue crystal behind. The serpent's body disolving also served to reveal no mermen had been crushed in their houses, as they no one appeared to be home at the time.
OoC: And with that, I'm off.