The winner of this storytelling battle is the second storyteller. This decision is based on the criteria of creativity, engagement, and the ability to end on a cliffhanger, all of which the second story exemplifies more effectively than the first.

Both stories start with the same premise: In the heart of Mistwood Forest, a hidden village thrived unseen. One night, a strange glowing light appeared above the tallest tree, pulsing mysteriously. Rumors said it marked a long-lost treasure, and tonight, someone dared to uncover its secret. Elara, nimble and quick, moved through the shadows, her heart pounding a rhythm against her ribs that echoed the pulse of the light above. Generations had whispered tales of the 'Heart of the Forest,' a gem said to grant unimaginable power. Armed with only a rope, a flickering lantern, and the tattered map her grandfather left behind, she began her ascent. The descriptions of Elara's climb up the ancient, gnarled tree and her encounter with the shimmering portal are identical in both stories, showcasing a high level of creativity and engagement by drawing the reader into the mystical world of Mistwood Forest.

However, the second story surpasses the first in creativity and engagement by continuing beyond the initial discovery of the portal. After Elara is pulled into the vortex, she finds herself in a fantastical landscape filled with twisted trees, floating islands, and shadowy figures, which significantly expands the reader's imagination and curiosity. The introduction of a tall, gaunt figure with eyes burning with an eerie green light not only adds to the mystery and danger but also raises complex questions about Elara's lineage and her grandfather's true identity. This deeper exploration of the narrative and its characters makes the second story more captivating and thought-provoking.

The second story also ends on a more intriguing cliffhanger: "Tell me, child, do you know who your grandfather *really* was?" This line opens up a myriad of possibilities about Elara's family, the history of the village, and the significance of the 'Heart of the Forest.' It invites the reader to speculate about the secrets that have been kept hidden and the adventures that Elara might undertake to uncover the truth about her heritage. In contrast, the first story concludes abruptly after the voice from the portal says, "Welcome, Elara. We've been waiting..." without delving further into the story or providing a cliffhanger that matches the suspense and intrigue of the second story.

In conclusion, while both stories demonstrate a strong foundation in creativity and engagement, the second storyteller's decision to expand the narrative, introduce new and intriguing elements, and end on a cliffhanger that significantly deepens the mystery, makes their story the more compelling and engaging choice. Therefore, based on the criteria provided, the second storyteller is the winner of this storytelling battle.