Senshi killed by the Shadow Galactica
The Senshi killed by the Shadow Galactica were the little-known Sailor Senshi who were never mentioned in the anime. In the manga, one of them appeared in a flashback and the others were only referred to by name. They were all killed to allow the Sailor Animamates to take their Sailor Crystals and become Senshi.
This Senshi was killed so that Sailor Heavy Metal Papillon could take her Sailor Crystal and become a Senshi herself. She was the Senshi of Cocoon. (Note: Sailor Cocoon was never named in any of the manga sources; her name is derived from that of her planet.)