Contribution:
The martial inclined monks of Eyros (I mean the ones who are the monks of the PHB) follow one central philosophy, that is derived from several sources and religious texts all over the world. They took from xalerian asceticism, elven mysticism and lizardmen connection to nature, shamanism and the good old orcs desire for fighting. The major influence were the techings from the lizardmen of Kohl´Tass, who contributed major parts of the philosophy and the martial art "Nature´s grasp". That technique became the foundation for the Dragon´s Way martial art practised by monks, today.
The monk´s way of life was formulated by the first monk, a human named Khyatil, a 1000 years ago, who was the first to combine the original lizardmen teachings with other philosophies.
A sentient being is made up from many parts, blood, bones, muscles. organsetc.. It is the same with the world. The world is composed of many parts that all work closely together, so the world is like one being, too. There is a connection between evrything and people are able to use this connection.
Mastering one´s mind and body is essential to enlightenment. If you are master of your own, you are able to use these connection between you and the other parts of the world and master your surroundings.
The monk´s martial discipline, meditation, a strict diet and general asceticism is used to master the body and the mind.
Besides this philsophy the monks often follow different religous beliefs and incorporate them in a central philosophy.
The different monasteries are sometimes at odds about certain interpretations and there is a yearly tournament in Eyrdeyn where monks of different monasteries compete and prove their point in best eyrian tradition. There is no central authority, each monastery is it´s own master.
Example for incorporating religious beliefs into the monk´s way:
The being Maia of the draconic legacy is often regarded as one of the primal souls of the world. The other sentient beings are tiny sparks of her as the world continues to grow. In death people return to the sacred lizards who are the memory of the world. The messengers are beings who achieved transcendence, beings in perfect harmony.
Taufenacht is regarded as another primal soul of the world, the one being filled with all the dark desires and lusts. People also carry a small spark of him within them. A true master seeks to purge his soul of Taufenacht and tries to be part of Maia only.
The unifying theory is mainly propagated from the monastery in Jazed´Khal. They believe that the creator is this world being and that everyone and everything is part of the creator.
The Praes Thanatos watches the monasteries closely, but realized that the monasteries are not organized enough to be a greater threat. Nevertheless, the necromancers keep a close tab on the monk´s activities, families and other loved ones just in case.
They are also a major patron of one gnomish monastery and monks from this cloister often work as bodyguards for the Patriae Sicarii and the gnome senators, when undead are not suitable, but an unarmed servant doesn´t raise an eyebrow. These are known as the Cestii Thanatos.
Monks are forbidden by imperial law to use normal weapons, because of security concerns. As most monks only show their skills in the tournaments, their fighting capabilities are not tested in war. This is an exception from imperial standard that all free beings are allowed to bear normal weapons, as the Senate felt uncomfortable, allowing an organized fighting force with their own fortress-monasteries to bear arms. To alleviate this they allowed the monks to have a selection of their own weapons, which the senate considers to be inferior.