Overall, I have enjoyed the spawn so far. It's challenging without being ghoulishly impossible.
The belt slot drop is a solid reward. It's basically a Crimson Cincture that replaces 5 Dex with 2 Mana Regen. If you're a caster wearing a Crimmy, chances are you weren't getting anything out of the Dex so this will help mana a bit. I think the developers have done a decent job addressing some of the armor slots that have less options (belt, earrings, talisman) through these temporary spawns and the 'treasures' events over the course of the last few years. Might not be best in slot, but definitely good gear for returning and mid-level players who are tight on gold.
And I'm a big fan of any rewards related to the Virtues / Anti-Virtues. The skulls with the anti-virtues with several different graphics - plus a few rare ones that will be sure to fetch a nice amount of gold - are better rewards than the last couple events, in my opinion. It would be great to see the developer's stick with this theme in future events.