Key fragment drop

it's not linear

It gets lower as the month progresses (Weird system imo)

It's not that the drop rate gets lower as the month progresses per se, so much as your odds decrease with each fragment you get, and the drop rate resets ~30 days after you get your first one. So your first key of the reset period is super likely even as a solo player, but if you spend all day playing, you'd find they became less and less common, so most will probably only get 8sih per 30 days. (I hear theres actually a cap of 12 per month too.)

Playing in a premade increases the drop rate though, so if you really want to maxmise your chances of getting a key fragment, you need to group. (Also, you can only get keys if you win, so keep that mind as well.)