The Heart Pane (`heart_pane`)

Scene: HeartPane. Camera: town style for the rim, with a wider overlook for cutscenes.
What it is: the last unbroken piece of the Mere, at the centre of the Shardfield. A flat mirror a few hundred metres across, sky above and below (Story Bible section 6).
Spawns: Spawn_rim_south (from the inner ring), Spawn_rim_underside (from the Undercrack), Spawn_pane_dawn (scene 4.12).
Exits: Exit_inner_ring (south-west, back to the Shardfield); Exit_undercrack (south, the Undercrack, once found).
Markers: Event_aske_fire, Mark_chorus_circle, Mark_ondine_tent, Event_rehearsal_crack, Mark_lantern_line, Mark_cut_line, Mark_lio, Mark_caravans, Event_first_pair, Mark_choice, Mark_heart. Cameras Cam_rim_overlook, Cam_pane_dawn, Cam_choice.
Landmarks: the chorus circle's four standing stones (west); the lantern line and the cut line (east); Aske's fire (south); the Waymaker wagons (north); the two hairline cracks running in towards the centre.
States: day (stage 2), night (stage 3), dawn (stage 4), day again from sunrise (stage 5 on); after the act, one state per outcome (stilled, shattered into a ring of standing pieces, cracked and held).
Rough layout:

                    N  Waymaker wagons (Mark_caravans)
                 .-----------------------------.
   Evane camp   /                               \   Facet camp
 chorus circle |  ~ ~ ~   THE HEART PANE   ~ ~ ~ |  lantern line
 Ondine's tent |  crack ---->  (Mark_heart) <--- |  cut line, Lio
   (west rim)   \        mirror, sky below      /   (east rim)
                 '-----------------------------'
              Exit_inner_ring    S  Aske's fire (Event_aske_fire)
                                    Spawn_rim_south / Undercrack

The player can walk on the Pane itself everywhere inside the rim. The rim is a ring path about 2 m wide where the camps stand on stone and shard.

From Walkthrough: Act 4 › Locations › The Heart Pane (`heart_pane`)