A summer afternoon. The sun was slowly hiding behind the line of the dark green forest, and a warm wind rustled the leaves. Michal, Lena and Bartek, three friends from eighth grade, had been planning this trip for months. The quiet forest behind their small town was shrouded in legends, but they were most fascinated by one place - an old oak tree with a split trunk. People said they sometimes heard whispers there or strange lights flashed in the middle of the night. Michael was the first to notice something unusual. Among the trunks, underneath the root of the oak, a mysterious symbol was shining. "Look at this!" he called out, crouching by the jagged ground. Lena pulled out a torch and illuminated the spot. On the bark, someone had carved a sign resembling a spiral with tiny stars around it. Bartek, always sceptical, tilted his head. "Probably the primary school kids were bored." But when he touched the symbol, the ground beneath their feet trembled. The air thickened, and a quiet, wheezing noise came from a gap in the tree. Everything around them began to blur, colours blended into a swirling kaleidoscope, and the friends' hearts pounded like mad. Suddenly, Lena froze. "There's... something behind that gap!" In a corridor formed of blue light, a door with mysterious, glowing hinges could be seen hanging in the air. They opened slowly, creaking ominously. Bartek looked at his friends, and there was a fear in his eyes like they had never seen before. "If we go in there.... we might not come back." But curiosity overcame the fear. Michael reached towards the portal, feeling a cold shiver run down his spine. At the same moment, there was a deafening metallic sound from behind the door, as if someone - or something - was trying to get to their side. The friends exchanged glances. No one was sure what to do. The portal opened even wider, and an unfamiliar light began to draw them in....