Best not expect a unique reward or anything other than the obelisk rewards. Sad when your actually telling yourself not to get excited for something on the road map. Undying mind 2.0? Looking at the road map my best guess would be that we will do sundial as normal but instead of going up the lift we will go through the large triangular door at the back of one of the sundial rooms shown on the road map and in there we will fight a different boss in a different Arena.