Catholics believe in "incorruptibility" as a sign of potential sainthood. This is where the body does not decompose. You can see the bodies on display https://en.wikipedia.org/wiki/Incorruptibility Catholics also believe in demonic possession, hell, and exorcism. Not the first things a priest will tell you though :)
Why wouldn't they tell you they believe in hell? It is mentioned in pray it was used to scare me into not misbehaving as a child by my teachers who were priests and nuns. This is not a secret nor did they try to hide it.
The Catholic Church has always believed in Hell. Jesus himself made reference to Gehenna (which was literally a valley of death back when he was alive, the Valley of Hinnom, where the Bible also documents child sacrifice to have occurred), as well as symbolically with the parable of the wedding feast. For this reason, many Catholic saints were themselves quite afraid of it and worked to avoid it.
Common misunderstanding though comes from "how could a good God sentence anyone to hell?" Well, to put it one way, he doesn't. Imagine if your teenage son violently doesn't want to attend your Christmas gathering. Would it be loving of you to force him to attend? Or, more graphically, imagine your son is a drug user who has lost home, family, girlfriend, and yet obstinately resists rehab - and you'd love for him to come, but he'd have to lay off the drugs, and he refuses any effort. Thus, the Catholic understanding is that the souls in Hell are obstinate in their sin and obstinately do not want to be in Heaven, for eternity because they will never change their minds. "The doors of hell are locked on the inside." They will, within Catholic thought, know they are in the wrong, but they would sin immediately again if they were permitted another second on Earth. This obstinacy in sin is mainly caused by refusal to repent for grave sins that have been committed.
This also explains, in a way, the reason why the Catholic Church in particular has very little hope in salvation for those who are atheist or similar.