Salve!
Here are some possible errata. Thank you.
ArM5 Core
p. 92. There are some phrases where it is said: "a Bjornaer", not "a Bjornaer magus / maga" as it should be.
Houses of Hermes: True Lineages
page 9: "In 1011, magi Trianomae convinced the Primus of House Guernicus to call an emergency Grand Tribunal instead of the Regular Tribunal meetings to deal with the situation." But in the Timeline (p.144): "1010. The inner council of Magvillus summons thirty Guernicus magi to the domus magna to perform the “Curse of Thoth” ritual." The year don't match.
p.143; The Leadworker Virtue says: "They may also make kolossoi that contain fixed arcane connections, taken from the bodies of their victims, without spending vis or study time." And after: "A Kolossos constructed with a sympathetic connection from the body of the victim imbedded in it (+3)". I think "arcane connection" should be used throughout.
Houses of Hermes: Mystery Cults
p.33. In the third column, first paragraph: “He needs to have a Rego Corpus Lab Total of 20”. It should be “Rego Animal” instead.
p.35. In the penultimate paragraph of the third column, the spell Speak with the Living Flame should be Words of the Flickering Flame.
p.37. "Bad Reputation" Flaw should be "Outsider".
p.43. In the "animal creation example: Bear" chart, in Qualities appear "Fast Runner", but not in the detailed creation.
p.67. “the avenue of Befriending the silent and the station that charms the elements”. The Target Level should be 21 - 3, for a total of 18, because it is the third Initiation since Major Ordeal.
p.86. "Inoffensive to (Beings)" in ArM5 is "General, Hermetic", not only "General".
Along the Verditius chapter you can read: “greater enchanted item”. I think it should be “invested item”.
p.125. Reforging Enchanted Items, first paragraph of the second column: “If his adjusted Lab Total is higher than the level of effect”. It should be “higher or equal”.
p.125. Third column, third paragraph: “If the total is higher than the level of effect of the power”. It should be “higher or equal”.
Guardians of the Forests: The Rhine Tribunal
Along all the book appears genius locus, but it should be genius loci.
page 21. The Arts of Trust of Childlike Faith are wrong, should be PeMe and the Casting Total +12; The Eye of the Eons spell should be Eyes of the Eons and InTe 10.
page 23. The Disguise ability should be Guile with a specialization in disguise.
page 23. Chaos of the Angry Wave should be level 30.
page 23. In the insert, Felicia is sometimes called Felecia (Felecia in p.85).
page 38. Immortality of the Forest is General, wouldn't it be better Supernatural?
page 43. "[...] 1220 the current duke, Dietrich III, dies and is succeeded by Matthew II." I cannot found Dietrich as duke of Lorraine, but Theobald I.
page 59. Philippus has Encumbrance 3(3), but only has clothes, dagger and longsword (total load = 1).
page 59. Chaos of the Angry Waves should be ReAq 30 not 20.
page 60. Apromor is named Apromar a couple of times.
page 73. Imanitos has Decrepitude: 0(2), but only 1 point in Qikness.
page 73. Imanitos should have dagger attack +3 (Dex -1, Brawl(dagger) 1(+1), Dagger Atk +2).
page 73. The spell Disguise of the Transformed Wizard should be Disguise of the Transformed Image.
page 73. The spell Recollection of Memories Never Quite Lived should be MuMe 4.
page 73. The total for Disguise of the Transformed Wizard (MuIm15) should be +24.
page 96. (again) Chaos of the Angry Waves should be level 30 not 20.
page 106. I think the encumbrance is wrong: half scale mail (4) + great sword (2) + lance (2) = 8 total load, hence burden = 3 and encumbrance = 2. Maybe the equipment should be full scale mail (load 7)?
page 106. Piercing Shaft of Wood should be level 10 not 15, and The Treacherous Spear should be level 25 not 15.
page 117. Hilda Short Bow Initiative should be -3, not -4.
page 117 Hilda Grapple damage should be n/a, not +4.
page 117. I think Hilda encumbrance should be 1 (full scale armor 7 + mace 2 + heater shield 2 + short bow 2 + pole axe 2 = 15, burden 5).
page 118. I'm not sure, but Crumena is a feminine latin name. Should it be Crumena filia Mercere instead filius Mercere?
page 119. Byrek: I think the Defense with Fist should be +6 (Brawl(fist) 2(+1) + Qik 3).
page 119. Byrek: the Encumbrance should be 3 (3). LOAD: long spear 3 + axe 1 + round shield 2 + heavy leather armor 3 = 9; BURDEN: 3, hence the initiative should be recalculated.
page 120. I cannot find anything about Longastisheim (near Bingen, at south). Could it be Langenlonsheim?