Used in scroll sprites for tracking what type of scroll it is currently doing, usually depending on $7E:1440/$7E:1441. This is the Layer 2 counterpart of $7E:1442.
It's also a castle destruction sequence text timer. Starts at #$FF when the 'Welcome' music starts, and a new line of text appears every #$20 frames after that. (#$DF, #$BF, #$9F, etc.)