1. Xykon will be killed, if only because his whole arc is about avoiding death and the Big Fire Below. I can imagine Xykon waking up there with the IFCC (and Belkar? Vaarsuvius? Tiamat?) there waiting to see him.

2. I think Xykon’s phylactery will survive log enough to realize he’s been betrayed.

3. Destroying the phylactery would leave Redcloak without a holy symbol, unless he has his backup handy. That might be interesting.