The Iron Armor was a suit of armor worn by Kain in Blood Omen; providing him basic protection against the threats of Nosgoth. The armor was subsequently shown in cutscenes in Blood Omen 2 and could be accessed ingame through several methods.
In Blood Omen, the Iron armor was the most basic of his armor repertoire, available at the start of the game along with the Iron Sword, it provided a decent all-round protection for Kain. The armour was originally worn by Kain as a Human before his transformation into a vampire and it was originally white in colour. Kain was wearing this armour when he was murdered by brigands and when the Necromancer Mortanius resurrected Kain as a Vampire, the Iron Armor was transformed along with him into its black and red form, noting the change in his armor Kain commented that it was now 'forged with hellfire' and was presumably now somewhat enhanced over regular armor.
In Gameplay, both the Iron Armor and its accompanying weapon the Iron Sword, were quickly superseded by more powerful and exotic weapons and armor; in FMV cutscenes however, Kain is still shown wearing the Iron Armor (along with the Iron Sword) right up until he made his fateful choice at the Pillars of Nosgoth and he is depicted wearing it in Blood Omen's 'bad' ending after the Pillars Collapse[Blood Omen].
The opening video of Blood Omen 2 briefly presents Kains 'dreamed' recollections of the Collapse of the Pillars; in which he is depicted walking away from the collapsing pillars wearing the Iron Armor and wielding the Soul Reaver. The Armor along with the Soul Reaver, could be 'unlocked' through a variety of methods including cheating, hacking and use of Bonus mode or the control station; the combination was extremely powerful and could kill virtually every enemy in the game in three strikes or less, though this is unlikely to be 'canon'[Blood Omen 2].
Defiance presented a brief cameo of the Iron Armor in its original form, as a portrait of Kain in his Mausoleum depicted him wearing it[Defiance]. The probably non-canon nature of Blood Omen 2's 'cheat' Iron Armor, means that Kain has not been seen with the Armor since the collapse of the pillars; It is unknown what happened to it following the events of Blood Omen and Kain seems to have abandoned it shortly afterwards.
The Iron armor is shown in Blood Omen to have originally been white in color (it was changed with Kain's transformation), suggesting it was the same type of armor as worn by the Ottmar's Army of Last Hope - Kain himself comments that Ottmar's throne once held his alliegance. The Iron Armor in its original form can be seen in a painting in Kain's Mausoleum in Legacy of Kain: Defiance[Defiance].
In the general gameplay of Blood Omen, both the Iron Sword and its accompanying Iron Armor are quickly replaced by more exotic and powerful weapons and armor; however in Blood Omen FMV cutscenes Kain is only ever shown with the Iron Sword and Armor combination, regardless of his current armor or weapon[Blood Omen].
In what was presumably a mistake by developers, the video depicting Kain walking away from the collapse of the pillars at the start of Blood Omen 2 originally featured Kain in the one-shoulder attire, before this was changed to the Iron Armor and Soul Reaver combination. Though, as noted above this may still be incorrect as in Blood Omen: Legacy of Kain's FMVs Kain combined the Iron Armor with the Iron Sword[Blood Omen].
The Iron Armor seems to have been intended to be gained upon completion of Blood Omen 2 (along with the Soul Reaver and a number of other features) in Bonus mode. This extra mode seems to have gone uncompleted, though the powerful Iron Armor / Soul Reaver combination can still be unlocked through other methods. The correctly entered cheat code plays a clip of Simon Templeman saying "Go Cheese!" - 'Cheese' was a nickname given to Blood Omen 2 lead artist Steve Ross during development of the game.
cut BO1 FMV featuring the original white Iron Armor
↑Kain:"Nothing is free."(Mortanius offers the transfixion sword to Kain. Kain steps forward and grasps the sword.) "Not even revenge"(Corruscating magic ripples across Kain’s body, transforming his white armour to black, living skin to dead vampiric flesh. Kain’s eyes open.)//Mortanius:"You will have the blood you hunger for..." Silicon Knights/Crystal Dynamics. Blood Omen:Legacy of Kain. (Eidos Interactive). (1996) Transcript.
↑Kain:"Iron Armor:As it was borne from hellfire, forged by the Necromancer’s magic, my armor resists fire and provides me with strong defense." Silicon Knights/Crystal Dynamics. Blood Omen:Legacy of Kain. (Eidos Interactive). (1996) Transcript.
↑ Crystal Dynamics. Blood Omen 2. (Eidos Interactive). PlayStation 2. (March 19, 2002).
↑"Willendorf, proud defender of the Realm, with its Warrior Elite and mighty ruler King Ottmar. The Lion Throne had once held my allegiance. But Willendorf’s days of glory had passed;it was the last bastion against an unruly future." Silicon Knights/Crystal Dynamics. Blood Omen:Legacy of Kain. (Eidos Interactive). (1996) Transcript.