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1. The Codex Mundane: Guilliman’s Tactical Break-Out Back to the Future by Valeryne40K (Valeryne)

   Fandoms: Warhammer 40.000  

   • Mature
   • Graphic Depictions Of Violence
   • Gen
   • Work in Progress

   06 Oct 2026

   Tags

   • Graphic Depictions Of Violence
   • Roboute Guilliman
   • Original Characters
   • Psychiatric Ward Setting
   • Psychiatric Medication and Drugs
   • Schizophrenia
   • Dissociation
   • Drug Use
   • reverse isekai
   • Guilliman finally get's Therapy
   • modern day AU
   • Fandom-Blind Friendly
   • Severe Depression
   • Therapy Arc
   • Existential Crisis
   • Dry Humor
   • Slow Burn Healing
   • Hyper-competence used poorly
   • Fish out of Water
   • Earned Recovery
   • Emotional Hurt/Comfort
   • Dark Comedy
   • German Humour

   Summary

   Roboute Guilliman, Primarch, Imperial Regent and Avenging Son of the Emperor, was built for cosmic destiny. He was not built for the 21st century, remarkably average height and a distinct lack of Power Armour.

   Following a rather rude temporal displacement, the universe has stripped him of his demigod status and dumped him into a German psychiatric facility. Where the doctors see a multi-syllabic litany of DSM-5 criteria, Guilliman merely sees an administrative nightmare.

   Armed with only non-slip socks and an involuntary prescription for sedatives, he faces his greatest strategic challenge yet: escaping a locked ward to save his timeline. The Imperium desperately needs him. But looking at this peaceful new world, a deeply heretical question arises: does he even want to go back?

   Language:

   English

   Words:

   36,313

   Chapters:

   10/?

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