Humans called it "the most painful thing known to medical science." Most ponies don't even know the condition exists because only humans are affected by it, and humans are either myth or long extinct.

However, a certain clan of Thestrals called the Vein clan know a lot more about the horrible condition the humans call "Cluster Headache" than they'd like to.

At first glance, the Veins appear to be an incredibly blessed family. About one in every three foals born to the clan has a horn and Earth Pony-like strength in addition to the bat wings that set the Thestrals apart from the other ponies. However, the "Thestricorns" in the family aren't nearly as privileged as most ponies think: Thestricorn members of the clan are born with a terrible curse, and when one is born, the parents grieve for the suffering their poor foal will have to endure their entire life.

(This fic is a tribute to anyone who has had to live with Cluster Headaches. As someone who suffers from them myself, I know full well how you feel, and my heart goes out to you.)