Much like in normal dnd, monks use ki (a vague concept that represents the innate force in everything) to do cool things. They get trained in monasteries, and all that. In this world, Wela, Deity of Time is the deity of ki and time, so it is usually the case that temples to Wela train monks, and that monks are worshippers of Wela. One big way that followers of Wela show their devotion is by sacrificing their TIME, which is why meditation is such a thing. That being said, monks can also simply be in tune with the forces of ki due to their own inclinations and contemplation, and they can be worshippers of other deities if they so wish.