As Pestilence says, you don't need any specific item, spell, NPC, or other external force. Regardless of your skills, spells, items, and party makeup it is doable.
As you don't want any hints as to what to do, I will answer your specific question about the big plates in the underground cellar you are in: "I just want to know if it can be done simply by pressing those big plates.". The correct answer is, "No, it cannot be done simply by pressing those big plates".
