Here's a summary.

Helga

Helga is a frog artist who gets a vision of the Sun Hawk, a Calamity Beast. As she runs off to report her vision, warning bells ring and Maha, the Night Owl, attacks Pondside village. Helga survives the attack and flees, heading to the nearest village to warn them of Maha's arrival.

Mabel

Mabel (the lead mouse) and her family are preparing for her birthday party. The nosy rabbit mayor prods her about bringing out her precious family heirloom (presumably Cragflame), but she refuses. Their conversation is interrupted when an exhausted frog shows up in town. The frog mentions an attack by a Calamity Beast, then collapses, unconscious. While rescuing the frog, Mabel wonders how she'll bring this up to her family.

Ral

On Ravnica, Ral is lying in bed, malding about Jace and what he did on Thunder Junction. Ral wants to kill him. With a clue from the Wanderer, he follows Jace's trail and planeswalks away. When he lands, he is shocked to find out he's been transformed into a literal otter.

"I'm going to kill him!" Ral shouted, his eyes filling with lightning as he shook his paw at the sky.