Tempest's End is a Sword Kit earned on Iki Island. You get it by finding every Memories of Your Father spot, and it changes your blades' look only.
Track down all the Memories of Your Father points on Iki. Finishing the last one hands over the kit.
Its theme is grief and reconciliation, which fits the Iki story about Jin's father.
A Scrawled Message
A Scrawled Message is a written record from the Records of Iki set, left by locals during the Mongol invasion. You find it at a camp south of Lake Nagata on Iki Island, and it counts toward the Avid Reader trophy.
Attached to an Old Crate
Attached to an Old Crate is a written record from the Records of Iki set, left by locals during the Mongol invasion. You find it at a shed northwest of Lone Spirit Fall on Iki Island, and it counts toward the Avid Reader trophy.
Image: Sucker Punch Productions / PlayStationBamboo Strikes
Bamboo Strikes are button-timing challenges where Jin slices a row of bamboo poles. There are 20 in all, 16 on Tsushima and 4 on Iki, and completing them raises your maximum Resolve.
Beware the Tengu-Masked Archer
Beware the Tengu-Masked Archer is a written record from the Records of Iki set, left by locals during the Mongol invasion. You find it at a house in Yahata Forest on Iki Island, and it counts toward the Avid Reader trophy.