Alteic is a language that originates from the Kingdom of Alterac. Unlike other languages, modern Alteic is an amalgamation of the many different dialects spoken during the time before the Empire of Arathor; when Alterac was largely unconsolidated or warring among the mountains. As a result, true Alteic is unknown, as many of these languages were completely lost when the Empire took over the region (aside from Fjoric).
Prior to conquering by the Empire of Arathor, the people of Alterac all spoke different dialects of a similar language. Referred to by linguists of the modern era as 'Root Alteic', the people of the mountain would see shifts in regional dialect every time wars would occur. Over time, only three dialects of Alteic remained in the mountain by the time of the Empire's conquering of the region (excluding Fjoric). Rather than continue to exist in different regions, the blend of the people of Alterac without conflict caused a merge of the dialects into what is now modern Alteic.
Given the fact that Ignaeus Trollbane had understood Thoradin when he came to the mountains of Alterac and brought the people of the mountain under heel; it is believed that old Alteic, or at least Ignaeus' dialect of it, was extremely similar to Common. Given that Common, and all Human languages, spur from Vrykul; it is not unrealistic to believe.
Alteic, despite its torrid history, ultimately was supplanted among its people for the language of Common by the Empire, as part of their plan to make a unified language for commerce. Though it survived among its people as a secondary language, the Second War that saw Alterac dismantled has left the language spoken only by its remnants and linguists.
Alteic is proxied by use of the Romansh language with a bit of German by the author, though people are free to use what they wish.