Yasto Attsmun was a tyrannical baron from Listehol who owned the yacht Undisputed Victor. During the Cold War between the Resistance and the First Order, he spent time on the planet Cantonica where he hosted parties every night aboard his yacht while sailing on the Sea of Cantonica. During one yacht party, the baron spoke with the arms dealer Jerdon Bly, who was murdered by Attsmun’s masseuse Lexo Sooger. In order to cover his escape, Sooger then spread word that there was a fire onboard the yacht, causing the baron and his guests to quickly evacuate. In the year 34 ABY, Attsmun was hosting another party on board his yacht where he made unsuccessful romantic advances toward the club owner Ubialla Gheal.

Attsmun was an alien with white hair. He was a tyrant who was not known for his generosity and never deigned to acknowledge servile beings or look at them. While speaking with Bly, he acted politely to the arms dealer but oozed contempt.