The breath of Gorgon petrifies on contact, so be careful.
There are some strong enemies here, such as Flame Demon and Beast Demon; check the strategy on their detail pages.
In the hidden room with a single Gorgon, you cannot dodge its petrifying breath if you stay at the entrance. Either throw a Crucifix as soon as you enter and take it down, or jump over it and attack from the left.
After defeating Adramelech (Iron maidens destroyed)
The path down from the middle section leads to Underground Gallery. The Underground Gallery is not required to finish the game, but the Heavy Ring there opens many routes, so on a first playthrough go there in order.