Ambrosia is a female member of the Grand Pegasus Enclave and was part of Harbinger´s group at Maripony. She spotted Littlpip seemingly fleeing Maripony and ordered her to halt. Littlepip tried to warn Ambrosia about the blast before it occured and then fled into a safe room. Ambrosia followed Littlepip, but didn't quite make it, she ended up locked in with Littlepip in the safe room, where she died from taint exposure.
Littlepip later recalls closing Ambrosia's face mask so she wouldn't witness the horrific contortions and changes the pegasus was undergoing.