When the egg hatches, the liderc is born. Where did the chicken go? We don't know. The liderc, however, will now proceed to fuck with your mind before literally fucking you. It will take on the appearance of a long-dead relative or lover. This is the part of the stories that I wish offered more details, because generally they go on to say how it comes back every night to bone you, and you start wasting away to death as it humps you and sucks your blood and sits on your chest so you can't breathe and that kind of inconsiderate monster stuff ... but for real, as a relative? Like, did someone's grandma do this to them once? You hatched this egg and it looks like grandma and now she keeps coming back to pork you to death? There's a lot wrong with this story. A whole lot.
Anyway, regardless of what and who the liderc looks like (Some stories say it has one chicken leg it keeps hidden in its pants. You know, so you don't get wise to how this dead sex partner of yours may not be all they seem), it'll keep coming back, either until you're dead or you find a way to distract it. How do you distract it? Random household chores! Keep that up for the rest of your natural life and you'll get through this OK.
Incidentally, there are also a couple of other lidercs out there. One kind is just a tiny devil that you might find in the pocket of old clothes, because maybe that's where you lost that little devil you owned? Anyway, find that liderc, and suddenly your life takes a turn for the better, as you gain fame and fortune and try to overlook the fact that the cost for these wonders is your soul. The other kind of liderc is just some flying fire or a will-o-the-wisp, which seems like the least menacing of the three at this point, and doesn't involve necrophilia.