Dayla was a female Kraylor.
She was a researcher who was part of the team that was experimenting with a cloaking device for the Kraylor ships. This device would protect the Kraylor ships against their enemy the Annari. After the captain of the ship was killed in a battle, Harry Kim took over as captain and tried to get the ship back to its planet. He thought that the ship was carrying a vaccine for the planet. Actually, the cloaking device was a prototype that the ship was bringing to their planet.
When the cloaking device on her ship became destabilized during an Annari attack, Dayla tried to repair it. She was able to bring it back online, but life support failed in the compartment and she died. (VOY: "Nightingale")