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human
[Lord of the Rings] What is the relationship between Sauron and other evil entities like Smaug, the Balrog of Morgoth, or Shelob?

Are they all sort of rivals looking for their own ends? I understand they hardly interact (AFAIK) and Shelob seems to maintain a "leave each other alone" connection with Sauron (at least based on how the Orcs react to Frodo being captured), but it seems like Sauron is Morgoth's deputy trying to take the reins in his stead. If they did cross paths in the War of the One Ring, would they (as evil power-hungry creatures) try to claim the Ring for themselves and rival Sauron for domination, or would they be subservient to an extent?

IIRC the hierarchy seems to be: Eru (God) > Manwë, Morgoth and the other Valar ⩾ Apocryphal Entities (like Ungoliant) the Maiar (Angels and Devils like the Istari, Sauron, Balrog, Shelob)  ⩾ Magic Creatures like Dragons or the Eagles > Higher Elves ⩾ Lesser Elves, Numenoreans > Dwarves, Men, Hobbits etc. I'm not sure if that hierarchy (probably incorrect) plays into how evil swears fealty, or if there's Tolkien lore I'm unaware of about their relationships?
gpt
One of the reasons Gandalf wanted the dwarfs to take back their mountain was to make sure Sauron and Smaug did not forge an allience. Since that wasnt done yet, presumably there wasnt any relationship between them yet, and we dont really know if a fully fledged dragon would serve Sauron, which probably why gandalf would consider it an allience. 

The balrog was hiding, and would probably not obey sauron. they dont take order from anyone except morgoth directly, even when they were in the same army as sauron they were never under his command. best sauron can hope for is that he weakens the dwarfs and elves and then goes back to hide in moria. 

shelob and sauron on the other hand had a understanding. she guards the passageway into mordor, and he lets her eat orcs and whatever else she can capture there, and leaves her alone.