Portal under the old oak tree

Timothy has always been curious, but he never thought that one ordinary afternoon would turn into the biggest adventure of his life. It all started when he and Lena, his best friend, went to the Old Forest on the edge of Green Corner. Summer was in full swing and the sun was dancing between the leaves of a mighty oak tree that, according to legend, was over two hundred years old. Tymek and Lena, bored with the daily attractions of the town, decided to search the forest for traces of the former inhabitants - perhaps some hidden treasures or mysterious signs. Suddenly, Lena stopped next to an oak tree and pointed to something strange. A circular depression had appeared in the roots of the tree, which had not been there before. In its centre glowed a pale blue whirlpool, resembling a moving sheet of water. Tymek bent down and touched the vortex - his fingers disappeared as if he had dipped them into a cloud! They both looked at each other with wide-open eyes. Was this the portal they had read about in books? Lena grabbed Tymek's hand. - "Let's try it together!" - she whispered excitedly. Before they had time to think, a vortex swept them inside. The world around them turned into a kaleidoscope of colours. The swirling mist descended and the children stood in the middle of a strange forest clearing. All around them grew trees with silver leaves, and the sky had two suns. From afar came an unfamiliar sound - something like singing and... the flutter of huge wings. Tymek and Lena only then noticed that a strange figure was hovering in the air in front of them. It had transparent wings and its eyes shone with a green glow. - Who are you and what do you seek in our world? - asked the being in a sonorous voice. The children looked at each other, unsure of what to answer. Behind their backs, the portal closed with a quiet clatter....