Why they promote it onShadowhuntersof course.
Sounds tricky, doesnt it?
Let me see if I can break it down for you.

Credit: John Medland/Freeform
Meliorn feels indebted to Clary for helping him escape the Clave.
As a thank you, hes willing to help her find her father.
He casually mentions that Clarys necklace is made of portal glass.
The portal this particular shard belongs to just so happens to be in an alternate dimension.
Meliorn can get her there using a magical door that is protected by the Seelie Court.
Jace is not happy about this arrangement.
Plus, there are no shadowhunters in that world.
Downworlders have conformed to regular mundane lives.
Theres no guaranteeing that shes going to get out once shes over there.
What if shes stuck forever?
Logic and reason are time wasters.
Suddenly, shes in her familys home eating breakfast with her evil father and kidnapped mother.
One of the shadowhunters details the ambush where they lost Meliorn.
Although vampires and werewolves were involved, hes quite confident he was bested by a shadowhunter.
All eyes focus on Izzy.
I think a few sessions of pre-marital counseling for these two is definitely in order.
Luke has to call off his pack when Simon announces that hes the new vampire ambassador to the wolves.
Luke tries to explain that being allies is possible, but its not going to be an easy process.
Especially when Simon still wants to snack from the neck of everyone around him.
Patience is a virtue.
And Simon isnt very virtuous right now.
Meanwhile, Simon in the alternate world is a doll.
His glasses are back, and hes dating Izzy.
An Izzy who wears Star Wars T-shirts and is a major technical dork.
One passionate kiss from Jace makes everything in Clarys world fuzzy.
She settles into the makeout session.
Then she remembers a TV spot showcasing physic reader Magnus Bane.
Hes her magical way out of this completely lovely and totally normal world.
She summons the courage to back away from Jaces advances so she can convince Magnus to help her.
Magnus isnt having it.
She draws pictures of demons.
Somehow, a few hastily drawn sketches unleashes the will in Magnus to try and restore his dormant powers.
Clary hands over the portal shard for Magnus to channel its powers, and his magic is restored.
He can see the portals location.
Its in the Institute.
Luckily, Clarys father is celebrating an anniversary party there that night.
Its a Mad Hatter theme.
Regular Magnus would have LOVED this.
I suspect he would have dressed as some retro version of the Cheshire Cat.
Remember the Internal Affairs guy who thinks Luke is a mass murderer?
Luke valiantly rushes in to save the day by shooting Simon 12 times in the chest.
Give this man a key to the city!
The Internal Affairs dude is relieved that the murderer is no longer a problem.
Lets put this down in the books as a win, guys.
While Simon and Luke are basking in their victory, Alec is developing a plan to save Izzy.
He wants to trade the Mortal Cup for his sisters freedom.
Well, he looked as outraged as Alec could look.
It was more of a mixture of boredom with a touch of anger, but you get the drift.
This is the last time Jace is going to cross him.
And if the bond breaks, so be it.
Jace is DEAD to him.
This news would have been more disturbing if Matthew Daddario hadnt been shirtless during this entire scene.
Alecs abs deserve a standing ovation.
The drama increases when Meliorn mentions that demons are attracted to dimensional doorways because they are peaceful and defenseless.
Two demons are attacking!
What are the odds that they would do this right when Jace is at his weakest?
Meliorn takes one down, and the other hops right through the doorway.
Demons at the Mad Hatter party?
Things are about to get crazy!
Or backwards at the very least.
Jocelyn and Valentine are like two kids in love.
Simon is asking Izzy to move in with him.
Alec is creeping on Magnus, and Jace is macking on Clary.
Once shes back, she and Magnus head to a secret door to find the portal.
Alternate Jace is super jealous and follows.
Real-time Jace pops up from his weakened state only to find Meliorn attempting to wrap up the doorway.
Jace begs him to go through.
Meliorn gives him permission and closes the door.
He disappears just as Alec and Lydia arrive.
Alternate Jace is pretty upset that Clary would choose to hook up with some random at her dads party.
He breaks up with her right when the demon attacks.
Cary gives it a nice roundhouse kick to the face while Alternate Jace cries like a baby.
Clary consoles her whimpering boyfriend.
Just when she decides that wimpy Jace is annoying, he transforms into the real Jace.
All he needs is a broom handle and that demon is as good as dead.
It was a great plan.
Except when the demons tentacle stabbed Jace in the neck.
That cant be good.
Magnus finds the portal and magics it open.
Jace slams down on the ground in Valentines warehouse, writhing in pain.
He draws a rune on himself to help with the venom, just in time to hear a noise.
Someone is trapped in a locker.
Jace carefully opens the door and pulls out his blade.
He stares in shock and awe.
I saw you die.
Clary wants to know what Jace is talking about?
Say hello to Jaces father.
The father that was supposed to be dead.
It looks like returning daddies are definitely a theme ofShadowhunters.
This just got really good.