The Realm of Water is ruled by Llyr Ap Mannanan, Lord of the Sea. The Element of Water is usually learned by those who are the most slow-tempered emotionally, those who move through life like the waves of the sea: they last longest, so they win in the end. The kind of person who would scheme for hundreds of year to become the power behind a throne and never once do people ever suspect...
Warning: Taking Dea'Tor in conjunction with Dea'Sil is a combination that should not be possible for the average sane person. If you are thinking about doing this, make sure that you mail Sol and make it very clear that you want both. He is almost certain to say no without overriding IC reason. The combination is simply too contradictory, and too powerful. If one of them is your third power, he will be somewhat more amenable, as at that point it's clear you are becoming a completist, which is somewhat different.
RP Tips: You just keep going and going. Repeat things a lot. Never, ever back down in a argument. Ever. Also, rarely if ever get angry, just be very very persistent. To the point of insanity: having an Obseessive Compulsive Disorder or three is a really good RP move for a Dea'Sil'n. Buy END. Those of you who haven't notcied the parallel I'm trying to draw with the continuous, everlasting wave action of the Sea need a cluecheck. If you do ever get angry as a Dea'Sil'n, make it huge. Make your anger reverberate throughout the land. Take a look at the Power of the Sea's Fury for tips.