Insane & erratic mages who are very resistant to Paradox & known for vulgar magick. When they appear they often cause Paradox that affects other mages. Thought to be associated with Dynamism at a fundamental level.
Blue Meanie is an interesting Marauder. Pg. 79 Digital Web 2.0. The Echo is interesting. Pg. 64 Book of Mirrors. Witch-House is cool pg. 247 Book of Secrets.
Sources:
Loom of Fate suggest Marauders are influenced by a single force of Dynamism or disruption in the universe. Later books suggest every Marauder is totally acting on their own.
The Chaos Factor pg. 116 takes an odd view of Marauders. “The Marauders, always good sports about these things, will move any incapacitated characters to another area”
Idea: When Marauder shows up, normal mage & Marauder both make Arete rolls. If the Marauder wins, local reality warps to Marauder’s view. If normal mage wins, reality is normal. One a tie, normal mage changes appearance to warped reality but knows it's fake.
NPC Idea: A Marauder who is quite sane but has an Avatar that is completely messed up. The Avatar has greater or lesser influence at times leading to the Marauder seeming sane sometimes but crazy other times.
Mage desire to escape Paradox attracts them to Marauders. This attraction makes Marauders more dangerous in the world of Mage.
Book of Madness Revised chapter 2 has interesting in-world theories of Marauders. Marauders may be a dualistic counterpart to Paradox, keeping the Tellurian from getting too static. Marauders may be possessed by rogue Paradox spirits that work against their brethren. Perhaps an inherently flawed Avatar forces a mage to become a Marauder.
A group of Marauders working together is a Conflux. Mage Storytellers Handbook pg. 54
Pg. 237 Mage20 core - Marauders sometimes form cabals. They are not known to last long. A fusion is when more than one Marauder share the same insanity. They work together well. A conflux is when Marauders work well in coordination but don’t share the same insanity. They often don’t realize they’re working together. Mages suspect outside influences of causing confluxes. When non-Marauders try to guide Marauders to do things it doesn’t work well.
Marauders are mages who have surrendered their agency and been filled with a force of nature. However, it isn’t a force of nature that Sleepers understand or can deal with.
Pg. 30 Infinite Tapestry says exposure to alien and harmful Umbral realms may have made some mages into Marauders.
Pg. 63 of The Red Sign introduces a new kind of “tome”. A book that can only be understood by people with Arete of 1 or more. A tome can teach an impossible, mind-bending Rote that gives the reader 1 or more points of permanent Paradox. This kind of book could be written by Marauders as a way of turning mages into more Marauders. A sort of recruiting. Reader may need to make a Willpower roll to resist a delusion planted in the tome.
Pg. 239 Mage20 core states Marauders above Quiet rating 5 are forced into the Umbra. They do not suffer disembodiment.
The Bigfoot Effect (Mage20 core pg. 240) makes technology ineffective at recording Marauder activity.
One question to consider is why can’t Mind Masters heal Marauders’ minds?
MY GAMES I don’t allow Marauder player characters. That allows me to say Marauders are 100% immune to Paradox. My idea is Marauders are created when someone gains a deep insight into the nature of reality. This insight causes them to completely understand Paradox and magic but the understanding is so shocking that the human mind becomes damaged beyond repair.