Dayak skull from Borneo, carved in pierced relief. Some Dayak tribes practised head hunting, i.e. the head of the defeated enemy was considered as proof of masculinity of the winner and forced the soul of the loser to serve the conqueror in the afterlife. Gruesome but every explorer should have been to Borneo.
Inca skull with signs of trepanation. Kinda reminds me of that line in the movie Ghostbusters: "Egon, this reminds me of the time you tried to drill a hole in your head." "That would have worked if you hadn't stopped me."