This summons Kosumoth the Hungering!
Go to Drak'thul at 37, 71 on Broken Shore Map and talk to him. Then go to cave at 57,52 on the broken shore and click the mud at the end of the cave to get the Weathered Relic you need. Then go to Drak'thul at 37, 71 on Broken Shore Map again and give him the relict and talk to him several times until he wants to leave him alone. After that click all the orbs in the right order!
1. 38, 37 Cave Aszuna
2. 32,75 Stormheim
3. 41, 80 Val'sharah
4. 32, 72 on Broken Shore Map
5. 59, 13 Cave Aszuna
6. 67, 14 on World Map, under the neutral shark is the cave entrance
7. 56, 38 Highmountain
8. 53, 26 Cave Aszuna
9. 49, 90 on World Map in the sunken ship
10. 37, 71 on Broken Shore Map
This will summon the Boss and give you a Worldquest to obtain the Fathom Dweller mount or the Hungering Claw pet! I think it changes weekly.
After clicking the last orb a region wide message appears:
Azeroth itself recoils as <name> unleashes an ancient evil.
Kosumoth the Hungering walks the land once more...