SPOILERS FOR CLOCKWORK PRINCESS.

Hi cassie! I’ve just finished TID and I’ve been wondering. Tessa is half shadowhunter, half demon, but someone (I think Mortmain but I’m not sure) tells her that her angel part “wins” against the demon part, so wasn’t she supposed to be mortal and die, like a shadowhunter? I know she is like a different race, but it still bothers me. Forgive me if that’s a stupid question. By the way, I love your books! Kisses from a brazilian fan.
— raissacouto

Helllo. Here’s what Mortmain actually said:

In you the blood of demons and the blood of angels has fought its own war in Heaven, and the angels have been victorious. You are not a Shadowhunter, but you are not a warlock, either. You are something new, something entirely other.”

So he is explicitly says “You’re not a Shadowhunter.” So there is no reason she would be mortal like a Shadowhunter or age like a Shadowhunter. She can’t bear Marks, like a Shadowhunter. She’s clearly not one. 

Tessa is a new and entirely other thing. No rules apply to her. There is no reason for her not to be immortal. There is no reason for her not to turn into a hot air balloon when she turns sixty and float to France. That would be very festive.

The Shadowhunters are often on about how their blood is dominant, by which they mean it’s dominant as far as they know —children born of werewolves and Shadowhunters, or faeries and Shadowhunters, or mundanes and Shadowhunters,  are Shadowhunters. But that is also because they are not too excited about the idea that there are things outside their experience. (Shadowhunter/demon hybrids.) Meanwhile, Tessa, being what she is, is immortal because there is no reason for her not to be, but her children aren’t — they do however have issues and powers out of the norm of regular Shadowhunters, which is something they must deal with as a difficulty during their lives.

More TLh art by the inimitable Cassandra Jean. If you haven’t read Clockwork Princess, don’t read on! Spoilery! I have also tagged this with cp2spoilers so it shouldn’t show up in your dash.

Two pairs of parabatai — Matthew and James above, and Cordelia and Lucie below. If you want to know about James’ glasses, he only wears them to read. :)