Someone who is serener is very calm and peaceful, especially when things around them are not calm.
Being serener is usually a very good thing. It means you can stay calm even when things are not good.
Examples:
She is the serener person I know.
The cat looks serener than the dog.
The serener the person, the better they can help others.
The serener the water, the more fish you can see.
He is so serener, he can sleep in a storm.
The serener the music, the more I like it.