Question: What fictional group created by Arthur Machen protected the British Army during the Battle of Mons?

Context paragraphs:
The Three Impostors: The Three Impostors; or, The Transmutations is an episodic novel by British horror fiction writer Arthur Machen, first published in 1895 in The Bodley Head's Keynote Series.  It was revived in paperback by Ballantine Books as the forty-eighth volume of the Ballantine Adult Fantasy series in June 1972.

We Are All Pan's People: We Are All Pan's People is an album by Julian House, under the pseudonym of The Focus Group.  It was released on 26 March 2007 on the Ghost Box Music label.  The title and artwork owe a simultaneous debt to the 1970s dance troupe Pan's People and the stories - the novella The Great God Pan specifically - of Arthur Machen; labelmates Eric Zann and Belbury Poly have also acknowledged a debt to the author.

Action at Néry: The Action at Néry was a skirmish fought on 1 September 1914 between the British Army and the German Army, part of the Great Retreat from Mons during the early stages of the First World War.  A British cavalry brigade preparing to leave their overnight bivouac were attacked by a German cavalry division of about twice their strength shortly after dawn.  Both sides fought dismounted; the British artillery was mostly put out of action in the first few minutes, but a single gun of L Battery, Royal Horse Artillery successfully kept up a steady fire for two and a half hours against a full battery of German artillery.  British reinforcements arrived at around 8 am, counter-attacking the German forces and forcing them to retreat; the German division was routed and did not return to combat for several days.  Three men of L Battery were awarded the Victoria Cross for their part in the battle, and the battery itself was later awarded the honour title of "Néry", the only British Army unit to have this as a battle honour.

Arthur Machen: Arthur Machen ( ; 3 March 1863 – 15 December 1947) was a Welsh author and mystic of the 1890s and early 20th century.  He is best known for his influential supernatural, fantasy, and horror fiction.  His novella "The Great God Pan" (1890; 1894) has garnered a reputation as a classic of horror (Stephen King has called it "Maybe the best [horror story] in the English language").  He is also well known for his leading role in creating the legend of the Angels of Mons.

Philip Howell: Brigadier-General Philip Howell, CMG (7 December 1877 - 7 October 1916) was a senior British Army staff officer during World War I.  He was, successively, Brigadier-General, General Staff (BGGS) to the Cavalry Corps under General Allenby (1915), and then BGGS to X Corps under Lt. General Morland (1915).  In October1915 he was posted as Chief of Staff (BGGS) to the British Salonika Army under Lt. General Mahon, before appointment as Chief of Staff (BGGS) and second-in-command to II Corps under Lt. General Jacob, forming part of General Gough's "Reserve Army" (Fifth Army) at the Battle of Somme in 1916.  Howell was killed in action at Authuille by shrapnel on 7 October 1916, after making a personal reconnaissance of the front line near Thiepval during the later Somme offensives.  Howell had been in action on the front line since the start of World War I, serving with the BEF, and commanding the 4th Queen's Own Hussars as Lt. Colonel through The Retreat from Mons, The Battle of Le Cateau, The Marne offensive, Hill 60, and the First Battle of Ypres.  He was mentioned in dispatches six times, and made a Companion of the Order of St. Michael and St. George(CMG) in 1915, for "meritorious service".

Great Retreat: The Great Retreat, also known as the Retreat from Mons, is the name given to the long withdrawal to the River Marne, in August and September 1914, by the British Expeditionary Force (BEF) and the French Fifth Army, Allied forces on the Western Front in World War I, after their defeat by the Imperial German armies at the Battle of Charleroi (21 August) and the Battle of Mons (23 August).  A counter-offensive by the Fifth Army, with some assistance from the BEF at the First Battle of Guise (Battle of St. Quentin 29–30 August), failed to end the German advance and the Franco-British retreat continued to and beyond the Marne.  From 5–12 September, the First Battle of the Marne ended the Allied retreat and forced the German armies to retire towards the Aisne river and fight the First Battle of the Aisne (13–28 September).  Reciprocal attempts to outflank the opposing armies to the north followed, known as the Race to the Sea (17 September – 17 October).

Charles Purdom: Charles Benjamin Purdom, usually credited as C. B. Purdom (15 Oct 1883 – 8 July 1965), was a British author, drama critic, town planner, and economist.  He was one of the pioneers and founders of the first garden cities, Letchworth and Welwyn Garden City, the latter of which he was appointed Finance Director between 1919–1928.  He was then made Honorary Secretary, then Treasurer of the International Federation for Housing and Planning (1931–1935).  He was also founder of the Letchworth and Welwyn Garden City Theatre Society, now the Welwyn Drama Club.  He won the Howard Walden cup at the Welwyn Garden City Drama Festival and the David Belasco cup in New-York in 1927.  He was an author of many books on city development, on Shakespeare and Bernard Shaw plays, Harley Granville-Barker, and on producing plays.  He was editor of an English literary periodical called "Everyman", covering books, drama, music and travel and featured articles by renowned authors such as Ivor Brown, Arthur Machen, G. K. Chesterton, A. E. Coppard, and Bertrand Russell.  He was General Secretary of British Equity (1939–1940) and joint secretary of the London Theatre Council.  He was also the earliest biographer of Meher Baba.  He was father of the actor Edmund Purdom.  He died in Welwyn Garden City in 1965.

Battle of Mons: The Battle of Mons was the first major action of the British Expeditionary Force (BEF) in the First World War.  It was a subsidiary action of the Battle of the Frontiers, in which the Allies clashed with Germany on the French borders.  At Mons, the British Army attempted to hold the line of the Mons–Condé Canal against the advancing German 1st Army.  Although the British fought well and inflicted disproportionate casualties on the numerically superior Germans, they were eventually forced to retreat due both to the greater strength of the Germans and the sudden retreat of the French Fifth Army, which exposed the British right flank.  Though initially planned as a simple tactical withdrawal and executed in good order, the British retreat from Mons lasted for two weeks and took the BEF to the outskirts of Paris before it counter-attacked in concert with the French, at the Battle of the Marne.

Angels of Mons: The Angels of Mons is a popular legend about a group of angels who supposedly protected members of the British Army in the Battle of Mons at the outset of the First World War.

Weird fiction: Weird fiction is a subgenre of speculative fiction originating in the late 19th and early 20th centuries.  It can be said to encompass the ghost story and other tales of the macabre.  Weird fiction is distinguished from horror and fantasy in its blending of supernatural, mythical, and even scientific tropes.  British authors who have embraced this style have often published their work in mainstream literary magazines even after American pulp magazines became popular.  Popular weird fiction writers included Edgar Allan Poe, William Hope Hodgson, H. P. Lovecraft, Lord Dunsany, Arthur Machen, M. R. James, and Clark Ashton Smith.

Supporting paragraphs: Arthur Machen Angels of Mons
Answer: The Angels of Mons