What's inside Gregor?

[MizasterJ]

I really have to wonder,did Qyburn use Dragonglass to make Gregor Clegane become a wight?  We did see some rather telling Text in screenshots from S7e1 where Sam is reading a book on Dragonglass and it says fragmented "ingestion, not harmful , cure for illness ,diseases"

We know he was thrown out of the Citadel, (probably by ArchMaester Ebrose) for trying to surpass Ebrose in studies of biology by doing "forbidden experiments". If the Citadel is probably the only place that has info on dragonglass, doesn't it seem most likely that Qyburn being so ambitious would have acquired it and attempted to use it? Also knowing what we know about Maesters and the probable conspiracy against magic that most certainly would be reason to give Qyburn the boot.

Futhermore Gregor does seem rather wightish, and the only other method we know of raising the dead is through the last kiss ritual , which seems very unlikely that Qyburn would perform on Gregor how else could he have possibly raised greg without the obsidian?  Now you are probably thinking how or where did Qyburn could have gotten his hands on Dragonglass. Well it wouldn't be that hard seeing as how they have Glass Candles made of it at the Citadel. Did Qyburn shove a glass candle inside Gregor?

That makes for an even more intriguing theory knowing how glass candles can manipulate dreams and communicate telepathically. Is the power Qyburn holds over Gregor the same the Night King has over the wights? 

[snow is the man]

In the books it is mentioned that people thought he dabbled in necromancy