The Vestments of Olorime comes in 2 versions, an imperfect and a perfect version. The perfect version is slightly stronger in terms of stats than the imperfect version (additional Magicka bonus). The 5-piece bonus otherwise does the same thing on both versions.
The Vestments of Olorime set is part of the Summerset Chapter. You can acquire the set in the Cloudrest Mini-Trial. Each set item is bound on pickup. You can acquire light armor, weapons and jewelry of this set. It uses the Welkynar motif style.