Sisela Ytheleus 1/2 was a type D4 military drone of the Explorer Ship Peace Makes Plenty, a vessel of the Stargazer Clan, part of the Fifth Fleet of the Zetetic Elench. It had a twin, Sisela Ytheleus 2/2.
When the ship was attacked by a powerful entity near a star called Esperi, it displaced its twin drone out of the ship and beyond the reach of the attacker, but not before surreptitiously copying its mind-state into its twin.
It was later attacked by the Affronter ship Furious Purpose, but managed to inscribe a message on its hull with a laser before self-destructing.