One of Stamp Guy's Stamp Stands on Hebra Mountain was swallowed up by a rift and he is hoping for some help.
Where to Start the Quest
Go to the highest point of Hebra Mountain and go east to the small rift. Talk to Stamp Guy to start the quest.
How to Complete the Quest
Check on the glowing spot in the rift, then check on the entrance to go into Stilled Hebra Mountain Passage.
Find Tri's Friends, Part 1
Go west and use echoes to reach an island with Snomauls on it. Defeat the Snomauls, but beware that there is a Freezard hiding in the ice blocks. Melt the western ice blocks and check on the glowing object to rescue one of Tri's friends.
Find Tri's Friends, Part 2
Go back to the east, then go north from where you entered the rift. You find a sideways pool of water. Defeat the dark Biri in the water, then go upward by holding B while in the eastern side of the water. Then when you're above the island in the middle of the water, create a stack of ice blocks that you can stand on to jump onto the sideways trees to the west. From there, go to the top of the island and put a fire echo on the glowing ice block. Check on the glowing object to rescue another of Tri's friends.
Find Tri's Friends, Part 3
Go south until you can go east. Defeat the Ice Keese above the icy ground. Go east, and beware of the Freezards in the ice blocks. Defeat them, and the dark Freezard drops a glowing object. Check on the glowing object to rescue the last of Tri's friends.
There will be a cutscene. Tri's level gauge will increase. You receive 2 Might Crystals.
Quest Reward
After the cutscene, you can use the Stamp Stand.