1) What does the fish consider a hero? I assume that's left vague for DMs to interpret as "PCs" but just a thought.

2) I think your HP is figured wrong... with 13 HD and +6 Con Bonus that should be 10+12d10+78, or 12d10+88. 4 more than what you gave it. Just a nitpick cause I was trying to figure out what 84 went evenly into, and couldn't think of anything, so I checked it >_>

3) I agree with seffbaslisk, the -1 Will Save could probably tempt players to try to mind control it... not a good thing.