Too many secrets

They started trekking once more, one step at a time. 

Soon, they reached the dead end. A giant metal plate blocked their entrance. Credence was going to put his hand on the door once again to melt a hole, but grandma stopped them from touching the iron door. She closed her eyes, then, for a brief flash there, the entire door shone with runes, save for a round spot. 

After she opened her eyes, Minah drew a small circle around this spot, then let Credence and Prudence melt the metal in the round shape, inside this circle. They did not cut a complete hole, but 'D' shape cut out, which hung out like a stair due to its own weight. After all, the door was eight inches of cold steel. 

After they entered the room, Abigail put her hands underneath this steel door, and pushed. Her mana almost came out of her, with how strongly she was using it. All the same, the cutout was pushed into place, afterwhich, the twins repaired the incision at the behest of Jung Minah.