Every year from October 30, Emerald takes this aspect temporarily (4 days), it is known as its Aztec spirit form.
This form is chosen by anyone who has in possession of the magic emerald that Emerald wears on her necklace, in this there is an ancient Aztec spirit, in which when October 30 falls, it frees itself and possesses the bearer of the magic emerald and neglects Emerald It is still the same only with a different appearance and a large evil face of the spirit in its big belly (Which by the way has life)

In this scene Emerald surprises some young people who were walking on a path at night and they see Emerald with her new appearance.
Don't worry, the boys are fine. Emerald wouldn't do anything to them despite their intimidating appearance.

This form only arises at night.