Yet more pics from the upcoming Horus Heresy Book 1: Betrayal:

Unknown Legionary in Mark III 'Iron' Armour only used in specialised units.

Empero's Children Legionary in Mark IV 'Maximus' Armour. Note: Leather pteruges added to standard armour as martial decoration (often worn as a privelage of minor within particular Legion companies).

An Emperor's Children Legionary and member of the Palatine Blades, an elite unit made up of the finest swordsmen in the Legion, tasked with seeking out and slaying the foe's finest warriors in battle. Note: Inclusion in these elite squads was often marked by the use of platinum blazoning of armour sections.

Empero's Children Decanus in Mark II 'Crusade' Armour. Note: Eye of Horus emblem denotes service with the Warmaster and possible lodge involvement.

Emperor's Children Decurio in older issue Mark II 'Crusade' Armour. Note: White enamel inlay used to denote rank and heraldry, an older Legion tradition dating back to before its unification with the Primarch Fulgrim.

Emperor's Children Prefectus. Note: Helmet crest which denotes status within the Legion's organisation, in this case membership of the elite 'Phoenix Guard' Millennial (Chapter)

Emperor's Children Centurion. Note: 'Phoenician' pattern helm (Emperor's Children Legion unique variant awarded as a badge of valour).Transverse helmet crest denoting senior rank.

Emperor's Children Apothecary.