Sorry but I just needed to write a little post about Erestor and religion because the tarot card inspired me...
He is often mocked for his piety, for being too extreme, for denying himself some most basic pleasures in life for fear that it will be sinful - and while he does indulge himself in vanity, it does frequently scare him that he’s doing the wrong thing, and as an elfling he did keep his skin clear and have his hair cut short (to his chin) as a symbol of rejecting pride.
He has made a vow of chastity as well as pledging his eternal life to Eru, Manwe and the holy Ainur. He regularly fasts to show self restraint, and will often reject indulging himself in alcohol and piperoot to show that he doesn’t allow himself to forget the Ainur by indulging in pleasures. He even prays for forgiveness if he does, just to make sure he hasn’t wandered from the light.
The Ainur and Eru do hear him every day, often praying to worship them, thank them, praise them, and apologise for any tiny potential wrong-doing he may have done.
He works as an advisor to Elrond so that he can make sure that everyone who lives in Imladris is fed, warm, happy, healthy, and essentially looked after the best that they possibly can. He greatly fears Sauron and the one ring, the darkness of the world terrifies him, even though he does his best to counter it.
In Imladris, the homage of the elves, it may seem ridiculous. He is very well-to-do, has a comfortable home, in a place where every single elf is looked after. Yet despite this he struggles to create relationships outside of work, being faithful to those he works for, and studying others, but making no true friends. He knows how to make allies - but not someone who will eat with him, or show him a flower just because they thought it was pretty, or stay up all night with him just because they thought he was interesting.
So he has pledged his life - thousands of years - to serving the Ainur, to serving Eru, to doing every single tiny thing that is written in order to be the best ellon he can possibly be in the eyes of Eru and the Ainur.
This extremeism may seem understandable in general for someone who grew up in a temple in Thargelion anyway, but let’s look at three quotes direct from the Silmarillion:
“On the house of Feanor the wrath of the Valar lieth from the West unto the uttermost East, and upon all that will follow them it shall be laid also."
“Ye have spilled the blood of your kindred unrighteously and have stained the land of Aman. For blood ye shall render blood, and beyond Aman ye shall dwell in Death's shadow."
"For though Eru appointed to you to die not in Ea, and no sickness may assail you, yet slain ye may be, and slain ye shall be: by weapon and by torment and by grief; and your houseless spirits shall come then to Mandos."
This passage ends with “The Valar have spoken.”
Erestor is a bastard, illegitimate Feanorion - but a Feanorion nonetheless.
This isn’t “you will go to hell if you are bad”. This isn’t even a vague threat of any kind.
This is pure and simple: “You will never be loved by the Valar and you will feel pain, torture for all eternity along with those you love.”
And other elves are confused as to why he is as pious as he is - he’s terrified to be anything but.