one of the greatest games ever made!
A: maybe we can use the wooden mask and insert the three new dragon priest masks inside of the sphere
B: The "fire from the deep" is the volcano across the sea and this fire burnt his house down and scarred the island, his friend came in after him to rescue him on his boat (now at the bottom of the ocean) and was murdered by bandits who stuffed him in the tunnel and the other man fled to his friends boat which was burned down by the volcano before he could escape (hence the burned ship in the bottom of the ocean with the dead body close by and the bandits remarking one getting away but "probably being killed by the ash spawn")
C: the fire from the deep on day 51 was really the ash spawn rising again and attacking his house and maybe the ash spawn spell will open it?
D: i dont know if this matters but i also noticed that if you go above ground and search about where the tunnel is underground youll notice where the bookcase starts is a mound above land showing his progress until theres a massive hill with some turned up rocks on top right above where the machine is, maybe we can get the excavation guy from raven rock to dig a hole down and uncover the sphere making an excavation site out of it. Idk but it sure is fun as hell making theories (this is when the community is strongest in my opinion is when were all helping eachother out trying to solve the nigh impossible).