So, we end the game killing a major creature, the Giant Eel! However, there is more to explore, and you have still not found the Angel of Hellwater. Is she simply waiting for your arrival with surprise and readied attacks? That would be bad. Does she have allies or summoned creatures ready to stand by her side? We shall see soon enough!
Unfortunately for Viceak there is a 42.6% chance that a character dies when the player is not present. Just speaking from history!
We can assume that she knows are here and will be ready. We should of course not only be cautious but ready our own attacks and I remind everyone those actions must be stated clearly to the DM... along with the trigger to launch the attack. For instance, "I have a readied spell (maybe flamestrike, or lightning bolt or whatever) to cast as soon as she appears"
Let's also remember to immediately do knowledge checks to see what we can find out about her...she may have immunities to such...