Hr'oln was Eve's first pet and also her password to The Museum of the Last Ones. She lived in a secret part of the Museum. When the Tenth Doctor and Martha Jones found her, she told them how she got there and how Eve was created.
She was an explorer for her species, the Cirranin, and travelled out into the stars. However, when she arrived home, she found out that her planet was destroyed in a war. She went out again, and landed on a planet. The inhabitants of the planet were afraid of her appearance, and so she built Eve to speak with them. The natives caught a plague, so Hr'oln tried to save them by developing suspended animation technology, but it was too late. Heartbroken, she told Eve that she must not let species die out. Eve then put Hr'oln into suspended animation. When she awoke, she declined the Tenth Doctor's offer to take her back to her own time, instead trying to save species by cloning different samples. (PROSE: The Last Dodo)