So, this is what worked for me.
Buy your boat from Jacob in Silvar for 500GP (tourist rip-off price!). Board boat, go north, take left fork, continue until you see gap in trees. Get off boat there. Follow the path north to reach the blood stain (go through tree at x11 y9).
Now, standing on the blood stain at x12 y8, look at the basalt wall to the east (x13, y8). You get a message saying the triangle fits into the odd niche in the wall - and a door appears one space to the north (x13, y7) of the niche.
I managed to find the amulet in the boot by bumping in to the stalagmite at x121 y21.