Where on the Avernus map is/do you place the Scab?  Frustrated I cannot find it on the map, thanks!

It's not on the map. I decided to place it near the lake of blood (where the Tower of Urm sets down).

Things that played into this decision for me:

• I decided Haruman's Hill overlooks the site of the Ride-- the perfect place for his prisoners to witness their shame for eternity.
• The Scab should be a reasonable distance for Lulu and Yael to flee from the site of the Ride
• A big ol' scab wouldn't look out of place near a lake of blood