Spectral Assault:
1. Go to the bottom where u get colors for ghost
2. In the middle stairs for leaving area there is endless void with only textures of stairs (no hitbox)
3. This was on onslaugh dunno if work on normal incru/trail/mastery

Altar of athame -
1. go into the candle inside building (this one on the top) - best one is in middle near fake door
2.Then jump into the corner of door (the spike on top of it) i will see textures above it
3. Jump over another spike outside the building
4. use double jump
5. Congratilations u are about the textures. Now u can place tree on bridge or go inside towers.

Thats something i found. hope it will help somehow. Also i can show this in game if there is need ^^
Also sorry for bad english.