Jarek's Vest was an orange vest that belonged to Jarek, who was a surviving member of the criminal organization known as the Black Dragon. Jarek's vest first appeared along with him in Mortal Kombat 4 and later reappeared as another collectible Relic in the Konquest mode of Mortal Kombat: Armageddon.
It was once worn by Jarek while he was still an apprentice during his early days within the Black Dragon organization.
Where to find it?
The vest is in Botan Jungle. Once you are near Argus' Temple you will have to fight members of the Black Dragon clan who are coming out of the little cement-made little boxes. Once you defeat all enemies, you will be allowed to open the boxes, and Jarek's vest can be found in the first one to the left.