Starting to detail the Thaggasoth Peaks.
The lighter brown usually suggests hills, while the darker areas with lines (not all have been drawn in yet) indicate the mountain building up elevation. The white areas are the snow line elevations. The light blue are ice or glaciers. The blue/green and purple are fungal forests. The usual green areas are typical tree forests.
The grey areas indicate hardened lava beds.
The castle/citadel markers and village markers represent those from the book.