Martio Batch is a human Grand Admiral, one of the twelve Palpatine created in 2 BBY, and a Star Wars Legends character. He earned the nickname "the invisible admiral" through a straightforward dislike of court politics, and after the Death Star was destroyed at Yavin the Emperor set him to producing a cloaking device that actually worked. His early hibridium experiments at the Imdaar Alpha research station hit the obvious flaw: the cloaked ship was invisible, and so was everything the pilot needed to see.
Around 3 ABY he used the superweapon Tarkin to crack open the planet Aeten II for the stygium crystals in its core, which made the cloaked TIE phantom possible. The Rebel Alliance destroyed the facility and the fighters. He fled to the Outer Rim after the Emperor's death and was assassinated by his own crew — loyalists of a commander he had had killed — who then defected to the Deep Core warlord Harrsk.
Catalogue entry. This figure has a verified record here rather than a full write-up — the encyclopedia labels its own depth instead of padding it.