This location is hidden away on a sandbar behind the island that holds Ysgramor's Tomb. Here is a large two-tiered platform; on the upper part is a Shrine of Talos, but on the lower part is a scene of carnage.
On arrival the Dovahkiin will be greeted by one living skeever. There are four more that are dead along with an Argonian Mage named Ilas-Tei. He is one of the missing Apprentices from the College of Winterhold and part of the broken side quest "The Missing Apprentices," which can be learned by speaking with Phinis Gestor at the college.
Ilas-Tei was practicing his Calm spell on the skeevers that he was keeping in a cage. You can find two Scrolls of Calm and a Scroll of Fury. He most likely was using the Fury spell to make the skeevers fight and then practiced his Calm spell. His practice this day did not go well.