You are an archmage tasked by the kingdom to slay a dragon, but there is a catch. The dragon is falling around the earth in low orbit, at such a speed that it is always directly above the city you reside in, it is durable enough to resist this while remaining conscious and in control. You are given the entire military force of the kingdom at your disposal to accomplish this. How would you go about slaying a dragon in outer space?
The spells you know are equal to a 20th level mage in DnD, so you can use 9th circle and below spells from that media, or things of similar nature. The kingdom has the same capabilities as a modern military of a regional power, albeit more magical. This dragon is as big as a mountain and can breathe fire twice its size.
Question: What is the element of the maze? Time, space, gravity, and void would be the best.
Time: Eternal time loop: (Dormamu, I have come to bargain.)
Space: Teleport to a distance place.
Gravity: Use meteorite to bombard and pull it to a star to make lizard fry.
Void: Again, some kind of internal prison.
The common four elements, along with thunder and metal, would be hard. But there is a way.
If your civilization's magic research is deep enough, then they might have something like '
star destroying ray.' (For the balance of power, it's better to design it in such a way that it would need a huge amount of magic crystal/energy). Also, you could use a magic power spaceship, load with a magic crystal bomb, and use it to do kamikaze attack, to wound the wings/ contain it/ or take it off the earth's orbit.
Hence, it might crash down on earth. However, remember, a mountain-sized meteorite wiped out all the dinosaurs. So you have to use a combination spell of earth and water to make a wide-area spell so that it could absorb most of the impact. Then it would be bombarded with all types of magical spells.
However, it would be nowhere near strong enough to kill a dragon. To do that, you need to use
a dragon slayer weapon, i.e. a weapon made of another dragon core or a dimensional weapon. And use that weapon to attack the reverse scale of the dragon. It is a good place to have a tear-jerking sacrifice.
But the most important thing you need to do is to find a way to counter all the attacks of the dragon.
P.S. Do the space dragon only breathe fire? If it is yes, then it is a fire dragon that can survive in space, not a space dragon. 
