Outside in the chill, those of you who made your spot checks see crimson beams of radiance in the sky that form a perfect square. For an instant the outline seems to show through to somewhere else, and then it's gone- but something vaguely humanoid is falling from where it was...
...then, in a flash, a dimension door opens beneath it and it vanishes through it.
Inside the cave, Lester pulls the figure from the egg. Covered in goo, it unfolds itself like a jack in the box, revealing a frog-like body of purple with brilliant emerald striations. Its head resembles some weird humanoid's- not human, not goblinoid, something different- and it sports bright red and orange feathered wings from its back.
As it stumbles from the egg, it makes a weird mewling noise.
The earth shakes, slightly at first.