The Secret Door Under the Stairs

It was a gloomy, rainy evening when Lena and her younger brother Adam were searching the cellar for board games. Their grandmother's house always hid lots of nooks and crannies and interesting objects - from old clocks to wooden boxes smelling of dust and lavender. Suddenly, Adam noticed something unusual. "Lena, look!" - he called out, pointing to a small, almost invisible door hidden under the stairs, behind a cobweb. The door was very old, all intricate patterns, with a strange symbol in the shape of a circle and three stars. They had no idea such a thing was here. "Maybe it's Grandma's secret stash?" - Lena asked, wiping the dust off the door handle. The door vibrated, as if it knew by itself that someone had found it. Without hesitation, Adam picked up an old torch and shone it into the darkness with concern. After a moment's hesitation, Lena pressed the handle. The lock squeaked and the door slowly swung open. Behind them stretched a long, narrow corridor, as if built of sparkling crystals. The air smelled of magic and something unknown. Adam took a step inside, and Lena clenched her hand tighter on the torch handle. Suddenly, a blue light flashed in the depths of the corridor. They heard a sound like wind singing and leaves rustling. The corridor, although it seemed empty, seemed to be calling them. "What's in there?" - Lena asked in a whisper. They both trembled as they saw a second portal slowly open at the end of the tunnel, shimmering with a thousand colours. Should they go in further? What was waiting on the other side? Their hearts beat faster as Adam, leaning against the corridor wall, accidentally activated a hidden mechanism. The portal flared even brighter, and swirling flashes began to rise around the siblings....