The structure of the obelisk must be repaired so it can be linked to the Sundial. Osiris believes some members of the Red Legion fled Mercury with tech pilfered from the Sundial. If you recover the components, you may be able to forge a link.
Defeat Cabal on the Tangled Shore to recover Sundial Components. Cabal defeated with Solar weapons and abilities may drop additional materials.
"Perhaps the Red Legion thinks they can recreate my work with stolen materials. If the situation were not so dire, that would almost be funny. The sooner you recover the components from their clumsy hands, the sooner we'll be able to restore the obelisk." —Transmission from Osiris
Legendary Quest Step
2019.12.10 (Season of Dawn)