I've been trying to remember this book series for the last couple of months and have had no luck. I can't remember any character names or locations, but I'll list everything I know! I read it in high school so anywhere between 1990 to 2014 were the publication dates, but it probably wasn't released that long ago nor ended in 2014.
It is not The World of Tiers series or Night's Dawn trilogy, but has aspects from both. The fantasy side from World of Tiers, but instead of different floors with different "worlds/ecosystems", it's different dimensions/universes. The invaders from the higher dimensions can come to our dimension because they can see below their dimension. We can go to their dimension with the help of magic to help us see, but without it we would become mad from the bright colors. I can't exactly remember what dimension they come from, but I think it's either the 5th or 7th.
The Night's Dawn trilogy comes into play because in the third book, there is a being called the "sleeping god". In the series I'm trying to remember, there is a god that needs to consume other beings because it's always thirsting for power, and I believe the god's followers get their powers from him.
The opening of the first book is a magician having a dream of the sea, and it quickly becomes a storm. He sees a warrior race from a higher dimension coming to kill them all in the 3rd dimension.
Besides the opening of the first book, I don't remember anything else other than a few details. They have to use magic to disguise themselves as the people from the higher dimension, and the last book has them at their capitol so they can infiltrate the castle to destroy the god below.
This probably won't help but it's the last piece of information I have. There is a certain part in one of the books which is from the perspective of one of the beings from the higher dimension (he is prophesied to help kill the god). It's a small fight scene where someone grabs his arm, so he pulls down on his hand while simultaneously sweeping his leg behind the guy to knock him to the ground. While falling, he grabs the guy's throat and slams him to the ground.
Any help would greatly be appreciated as it was one of my favorite books while in high school.