Tria

Paladin Tria is a Paladin. She's the first and only female Holy Knight shown in the order.

Volume 4
She was escorting Lumachina to Faltra City but were attacked by Gewalt. She was defeated and captured by his Trap Worm but luckily Lumachina was saved and got away.

Volume 6
She was revealed to have been imprisoned in one of the prison cells by Gewalt when he gave the key to her cell to Rem.

Lumachina Weselia
Tria is very loyal to her.

Trivia

 * Tria is the only Holy Knight that is not evil.