The Creator God and also Tears to Tiara's version of the Abrahamic God, He takes no direct action in the story. It is theorized that He either has no concern for His creations on Earth, or that He is not troubled by the actions of the Angels. It is also implied that He may not exist at all, but is only a lie or just a fabricated religious system created by the Angels, although this does not fit with certain dialogues in the story. According to Myrddyn, the Angels do not completely understand the will of God, leading to the possible conclusion that Watos created Arawn, the imperfect Thirteenth Angel to try and change the attitudes of the other Angels. If so, then He may be concerned about events on Heaven and Earth, but is unwilling to directly act on these events.
Watos' symbol is the Sun, as depicted in a mural in Arawn's tomb (according to Octavia, this symbol is also used by the Holy Empire). At several points in the story, the sun is shown in full, implying that He does watch over Creation. One such moment was the last episode, after the Words of Power crippled Merkadis and exposing frail and naked Lector, he desperately raised his right hand to the sun and begged Watos to rescue him.
It is possible that the Words of Power is addressed to Watos, as when Rhiannon completed the spell a blast of Golden Light even more powerful than Merkadis descended from the Heavens. Considering that the Angels prefer white and the only other being in the Heavens is Watos, it is possible that He will act if asked by His creations on Earth, as implied by the last verse of the Words of Power, dona nobis pacem, grant us peace. The same is also applied to another holy magic, Candidus, which among the chant is to give the user "a perfect world" and the Angels prayer contain these verses.
If the Power of Words is connected to Watos, it is possible that Watos grants Rhiannon the knowledge of this magic, as Rhiannon receives a vision where she is united with those she cares and through this vision she finally able to remember the incantation. Then, the spirit of Primula tells her that the knowledge of Words of Power was within her all the time. So it is possible that the vision was shown by Watos to aid her utilize the magic so that His creations may be saved from Merkadis' wrath (and to pass judgement on Lector as well). Watos' refusal to rescue Lector seems to support that He sided with His creations and cares for them.