I donated a music block to Humbaba and my screen popped up with notifications about reaching 1,000 favor points with a whole bunch of giants! It also brought me up to level 13 when I had only just reached level 12. When I check my favor points with Humbaba did not have 1,000, but I appear to have 1,000 with the other giants now. I just checked at a shrine to Pot and got an emblem.