The HoloXer Masks are made at the projection cube in the simulation room, they are only craftable for a limited time, and allow you to get into the new area

Info for crafting is up on the wiki.

So I've been experimenting for a few hours and honestly I'm kinda lost. Tried to search elemental disadvantage/advantage but there's no concrete evidence except to actually try it in game so I did somewhat messy experiment

Basically fire is advantageous against most mobs we'd actually need (Wolf, Boar, Deer, Sheep)
Wind is slightly advantageous vs water slimes (I tried a fire skill vs water skill its like 40 damage difference my fire sword has 57 fire damage while wind sword has 25)
Ice will kind of oneshot the fire slimes if you had the strongest skill book (and it will also deal 25 DoT to fire related mobs like Mandragora)
Water has not enough data for me, I remember it dealing same damage to Huge Slime while also dealing decent on normal mobs
I dont have thunder because I switched it with another element (Please devs separate skill books with enchants!)

I'm pretty lost on this if anyone has data about elemental weaknesses it could help thank you!

Don't miss out on those Holocentives!