After completing the Ketheric Thorm questline and clearing Moonrise Towers, the next step is to locate the Road to Baldur's Gate Waypoint.

Source: https://gamerant.com/baldurs-gate-3-act-three-location-third-act-guide-bg3/

"Beneath the smoking ashes of Moonrise Towers, the elder brain lies destroyed," the narrator says.

Source: https://www.digitaltrends.com/gaming/baldurs-gate-3-patch-1-details/

Infiltrating Moonrise Towers, recruiting companions like Jaheira or Minthara, and rescuing prisoners are important to progress the story and end the shadow curse.

Source: https://gamerant.com/baldurs-gate-3-bg3-things-do-before-going-act-3/

Squire the skeletal hound in Moonrise will no longer try to call for guards once the assault has started.

Source: https://gamerant.com/baldurs-gate-3-patch-5-epilogue-new-game-mode-patch-notes/