The Principality of Daimar'Yar was a short-lived High Elven state found in Polforia, during the Middle Human Age, existing between the 2228 to the 2254 a.a.H. It's often considered one of the Polforian states and a late attempt of High Elf imperialism, but it wasn't connected by land to the other human-elven states of the Outregam.
While in the Outregam was achieved some compromises between the High elves' supreme commander Saerchanar the Fake and their human allies for a joint colonization of Polforia between humans and elves; members of the White Party of the Empire of Whide Axis, angered by the humiliation of Saerchanar, decided to found an unsanctioned High Elven realm in Polforia, acting in an independent way from the joint colonization project:
An expedition of High Elves arrived then at the Seven Cities of Daiman'Yar -a vassal blood elven state of the former Dark Legion of Demons-, and will proclaim the Principality of Daimar'Yar -a small cosmetic change to avoid a direct reference to the demons-
The High Elves, forming a military nobility, attempted to organize the Seven Cities as a Principality of the Empire of Whide Axis, "saving their cousins from demonic corruption", wanting to use as well the important ports for a later expansion to the interior of Polforia from the sea, while supposedly the other elven colonies of the Outregam, Tahela, Avaynti and Reivelin, were meant to progressively advance eastwards, strengthening the position of the Empire in Aels:
However, the Principality was never recognized as a dependence by the Empire of Whide Axis, which was then without an Emperor and de-facto ruled by the isolationist Purple Party. As well, an independent high elven colonization attempt in Polforia, aside of the agreement achieved with the Five Kingdoms, was seen with distrust, lacking therefore support from them and the Outregam Polforian states, aside of some individual colonists.
Aside of these exterior problems, the High Elven elite ruled with an iron fist over the Blood Elves, persecuting non-elves, Doroz and Half Elves out of the Seven Cities of Daimar'Yar: this will spark rebellions in a population who first had received the High Elves as their liberators.
They will face rebellions of the Blood elf peoples they sought to rule and 'redeem', and attacks from the demonic remnants: by the 2254 a.a.H, the last high elven hold of the seven cities of Daimar'Yar will all but disappear.