The Second Wizarding WarEdit
Three of the founders' relics were destroyed because Voldemort's soul was sealed withing the relics. In order to defeat the Dark Lord, Harry Potter and his friends must destroy these relics and make Voldemort vulnerable. Harry Potter managed to destroy the Diadem of Rowena Ravenclaw (with the help of Fiendfyre by Vincent Crabbe), Ron Weasley destroyed the Locket of Salazar Slytherin and Hermione Granger destroyed the Cup of Helga Hufflepuff.
The Relics Found and Hidden Again Edit
After 10 years, the professors retrieved the relics in these places: the locket in the Forest of Dean, the cup in the Chamber of Secrets and the diadem in the Room of Hidden Things. They decided to hide it deep inside the castle and castle grounds so no one can use it again for evil. It is said that the Locket of Slytherin was hidden deep beneath the Chamber of Secrets. The entrance to the Chamber was changed from the bathroom sink in the second floor to a hidden door in the dungeons with multiple magical locks. It leads to an underground tower that was discovered 5 years before the Locket was hidden. The inside of the tower is intact and hollow and is said to be the home of the Kraken, an ancient sea monster. There are multiple obstacles to keep the Locket safe. The obstacles are unknown but one is known: a giant stone maze. The Cup was hidden somewhere at the very bottom of the Black Lake. There is an underwater chamber that is very, very well hidden. It leads through a series of chambers with dozens of riddles that must be answered to pass. The Diadem was hidden in the Room of Requirement, but not in the Room of Hidden Things. The way to the Diadem is very dangerous and deadly, as it is like a journey outside the school. The path is blocked by very difficult tasks and very violent creatures. Only a miracle will happen if the thief gets out alive.
The Sword of Godric GryffindorEdit
The sword of Gryffindor is the only relic that is not found or hidden. It only appears to a true and worthy Gryffindor and only when truly needed. But when a Gryffindor uses it, it does not make him/her the owner of the sword. The sword may present itself to any worthy Gryffindor. Thus, the professors did not hide it.