It's through email, I'm sure they have the format in a FAQ on their website somewhere. Everybody has a chance but I'm pretty sure they just picked 2 North American mods
Seal of the damned actual drop rate is 3%. Hence why people don't see them that often horns drop 5-10% of the time other than that there's not much to present other than the following data
Since the drop release out of 100 haunts I did b2b 3 times a seal dropped whereas 7 horns dropped some dropped two horns at a time.