Legions Imperialis – Adding a Legio, Knight House or Auxilia to your Loyalist Legion

In Legion Imperialis you have the opportunity to use combined forces, so not just Astartes but field them with support of Knight Households, Titan Legios and Imperial Militias or Auxilia regiments. But which Legiones Astartes fought alongside which of those and what would create a proper alliance according to the lore?

Of course, you can do what you want, it is your hobby, but with the Horus Heresy community known for being fluff bunnies, this is something I wanted to share with you, based upon lists from the fan wikis and combined work by people like David from Cat Hair in the Paint Pot.

I merged the lists and linked the according information from the wikis, so you have it at hand by looking up your Legiones Astartes. Beginning with the Loyalists. With the exception of the Raven Guard, every loyalist legion fought at one point along side the Legio Gryphonicus (War Griffons) and each of them can use the Solar Auxilia without any doubt.

The 1st Legion, the Dark Angels from Caliban, already have the opportunity to bring their troops in Black, Green or White, but are able to field an even broader variety with the following affiliated factions.

Supported by Titan Legios: Legio Astorum (Warp Runners), Legio Gryphonicus (War Griffons), Legio Solaria (Imperial Hunters)

Affiliated Knight Houses: via Gryphonicus (Cadmus, Coldshroud, Fvaber, Klaze, Vyronii), via Astorum (Hawkwood, Mortimer, Terryn)

Affiliated Auxilliaries and Imperial Army: Solar Auxilia, Caliban Jaegers

The 5th Legion, Jaghatai Khan's White Scars, Loyalists, fought among other campaigns on the Siege of Terra.

Supported by Titan Legios: Legio Astorum (Warp Runners), Legio Atarus (Firebrands), Legio Gryphonicus (War Griffons), Legio Ignatum (Fire Wasps), Legio Solaria (Imperial Hunters)

Affiliated Knight Houses: via Gryphonicus (Cadmus, Coldshroud, Fvaber, Klaze, Vyronii), via Astorum (Hawkwood, Mortimer, Terryn), Megron

Affiliated Auxilliaries and Imperial Army: Solar Auxilia

The 6th Legion, the Vlka Fenryka, better known as the Space Wolves, Loyalists

Supported by Titan Legios: Legio Astorum (Warp Runners), Legio Gryphonicus (War Griffons), Legio Ignatum (Fire Wasps), Legio Mortis (Death's Heads) - at Prospero, Legio Solaria (Imperial Hunters)

Affiliated Knight Houses: via Gryphonicus (Cadmus, Coldshroud, Fvaber, Klaze, Vyronii), via Astorum (Hawkwood, Mortimer, Terryn), Megron, Malinax

Affiliated Auxilliaries and Imperial Army: Solar Auxilia, Terranic Auxilia, Charonid Sentinels, Host of Brass, Sarcosan Voltigeurs, Ydranian Seekers

The 7th Legion, the Imperial Fists under the command of Rogal Dorn, Loyalists

Supported by Titan Legios: Legio Astorum (Warp Runners), Legio Gryphonicus (War Griffons), Legio Ignatum (Fire Wasps), Legio Invigilata (Emperor's Guard)

Affiliated Knight Houses: via Gryphonicus (Cadmus, Coldshroud, Fvaber, Klaze, Vyronii), via Astorum (Hawkwood, Mortimer, Terryn), Megron, Hermetika

Affiliated Auxilliaries and Imperial Army: Solar Auxilia (789th "Ice Bears" Solar Auxilia Cohort of Inwit, Manachean Bulls), Chalchidean Grenadiers

The 9th Legion, Blood Angels, Loyalists, one of the legions who brought their greatest sacrifice and lost their Primarch to defend the Emperor.

Supported by Titan Legios: Legio Astorum (Warp Runners), Legio Atarus (Firebrands), Legio Crucius (Warmongers), Legio Fortidus (The Dauntless), Legio Gryphonicus (War Griffons), Legio Ignatum (Fire Wasps), Legio Solaria (Imperial Hunters)

Affiliated Knight Houses: via Gryphonicus (Cadmus, Coldshroud, Fvaber, Klaze, Vyronii), via Astorum (Hawkwood, Mortimer, Terryn), Devine, Donar, Indra, Kaushik, Marmaragon

Affiliated Auxilliaries and Imperial Army: Solar Auxilia

The 10th Legion, Ferrus Manus' Iron Hands, Loyalists, one of the three shattered legions.

Supported by Titan Legios: Legio Agravides, Legio Astorum (Warp Runners), Legio Atarus (Firebrands), Legio Gryphonicus (War Griffons), Legio Ignatum (Fire Wasps), Legio Solaria (Imperial Hunters),

Affiliated Knight Houses: via Gryphonicus (Cadmus, Coldshroud, Fvaber, Klaze, Vyronii), via Astorum (Hawkwood, Mortimer, Terryn), Hermetika, Megron, Callivant, Col'Khak

Affiliated Auxilliaries and Imperial Army: Solar Auxilia, Dogan Maulers, Veridan Korracts

The 13th Legion, protecter of the Five Hundred Worlds, Ultramarines, Loyalists.

Supported by Titan Legios: Legio Astorum (Warp Runners), Legio Crucius (Warmongers), Legio Fortidus (The Dauntless), Legio Gryphonicus (War Griffons), Legio Ignatum (Fire Wasps), Legio Lysanda (Sentinels of the Edge), Legio Oberon (Death Bolts II), Legio Praesagius (True Messengers), Legio Solaria (Imperial Hunters)

Affiliated Knight Houses: via Gryphonicus (Cadmus, Coldshroud, Fvaber, Klaze, Vyronii), Devine, Donar, Hermetika, Indra, Kaushik, Marmaragon, Megron, Vornherr

Affiliated Auxilliaries and Imperial Army: Solar Auxilia (Calth High Guard), Ultramar Defence Auxilia, Praecental Guard, Highborn Wardens, Numinus 61st

The 18th Legion, Salamanders, Loyalists, who lost almost their entire legion on Isstvan V.

Supported by Titan Legios: Legio Agravides (Battle Scourges), Legio Astorum (Warp Runners), Legio Atarus (Firebrands), Legio Gryphonicus (War Griffons), Legio Ignatum (Fire Wasps), Legio Solaria (Imperial Hunters)

Affiliated Knight Houses: via Gryphonicus (Cadmus, Coldshroud, Fvaber, Klaze, Vyronii), Hermetika, Col'Khak

Affiliated Auxilliaries and Imperial Army: Solar Auxilia

The 19th Legion, Corvus Corax' Raven Guard, Loyalists

Supported by Titan Legios: Legio Adamantus, Legio Agravides (Battle Scourges), Legio Astraman (Morning Stars), Legio Atarus (Firebrands), Legio Nivalis (Ice Giants), Legio Vindictus, Legio Victorum (Foe Slayers)

Affiliated Knight Houses: via Atarus (Arakon, Col'Khak, Vornherr), Hermetika

Affiliated Auxilliaries and Imperial Army: Solar Auxilia

If you want to see it the other way arond and already a Titan Legio from Adeptus Titanicus, you can look up feasible allies for the Loyalists here.