I need a huge castle that can hold of vast numbers off invaders, there is magic, medieval tech

Question

I have a huge castle, more like a walled city, population 70,000. About one thirds of those are fighting age and men. The castle is built on a huge mountain, which is flat at the top, about ten square miles. There's only one way up the mountain, a winding ramp that goes all the way around the mountain. (The top is directly above them bottom.) There is magic, but very few have enough power and knowledge to wield it well; about 100. The castle has a force of cavalry 3,000 strong, and they're trained on charges down the slope(the winding path that goes around the mountain that the castle is on top of.) The defenders have enough food and water to last them years, and they keep on growing things so scurvy isn't a problem. They also have trebuchet at different positions on the wall and distributed around the city.

Explanation of Magic

Magic is a second life source. If you run out of it you die.

The less Magic you have the weaker you get. In this respect it is like a second stamina.

They way your body checks if it is physically strong enough to do something is as follows:

• It checks if your body has enough stamina and Magic
• The stamina is used up, but the Magic is not

When you use Magic that changes as follows:

• You don’t need stamina

Magic has two ways of doing something:

• on release
• on impact

If you were to light a few sticks of wood on fire and you wanted to do it with magic, you could:

• send out the Magic (still in Magic form) and when you hit the pile of sticks, you can turn the Magic into the fire

OR

• Make a small flame that shoots toward the sticks and lights it on fire when it hits

Some spells can be both, but some are only on impact.

If you send a spell to paralyze your enemies (make them unable to move) there is no way, unless maybe send a spray of paralyzing poison toward them, to do it on release.

Everyone in this universe has Magic. Some people produce more Magic than others. This is the reason that few can do great feats of Magic, though if they knew how, almost anybody could conjure a candle-flame.

Another thing that you need to know about Magic is the use of it. Special words, the Olde Tongue, were linked to the usage usually, but not always. The words just helped you to focus and ‘stay on target’. These words helped magicians to focus on what they were doing and not get lost in the process.

The Enemy

They have about 100,000 soldiers land, about half are conscripted so they don't really want to fight and don't have good training, other half are expert soldiers, about 10,000 are mounted, the rest are melee or archers, about half and half, also archers have low bows, not crossbows. Enemy have about 200 mages. The enemy also have a Sky Force of about 12,000.

Enemy Sky Force

500 Dragon Riders: dragons are about 80 ft. long, can breathe fire, have deadly whiplash tails, aren't smart.

500 Griffin Lancers: men with long lances, land in the middle of the city and wreck havoc, griffins aren't smart but listen to commands, about 50 ft. wingspan.

10,000 Transported by Rocs: men who will be dropped in the middle of the city by a roc, they ride in carts, but if safely dropped, cause mayhem, trying to open gates and letting the rest of the army inside. They are distributed among 100 rocs, 100 to a roc.

1000 Gargoyle Trainers: stay on ground but set gargoyles, (almost as smart as humans,) onto people, gargoyles are demonic things that can turn into almost unbreakable stone, and then turn back at will, so they are great bombers, bombing themselves onto prominent buildings and troop forces, can be broken by some magic spells.

As you can see, it'll be a hard fight for my defenders so I need some really good defense ideas. What'll help the defenders win?

Answer 1

Against the air raids you want strong metal gridiron above the Streets. Make the bars about 8-10 inches apart, an inch or two thick. That would prevent the enemy from landing within your fortress. Except perhaps a mustering ground in the center that would be well guarded.

This would block the gryphon lancers and rocs from dropping men within your fortress. Just make sure to have a barracks next to any open squares. Perhaps even those could be covered with pillars supporting the gridirons.

Next you want retractable wooden ramps bear your gate. Removing those bars the enemy from attacking your fortress head on as they need to spend time and resources fixing the ramp.

For the gargoyles I'd say focus the mages on them. Specifically turn them onto ice and watch them shatter on impact. If magic is unable to stop the gargoyles you will need to suffer them much like the British suffered the German V-missiles in World War 2.

Same thing applies to your dragons. I say focus on the riders. Dragons appear to be to dumb to continue fighting without their rider. Magic should allow you to hit the riders themselves. Barring that keep everything wet so it doesn't burn so well.

Perhaps go the Dwarven way and move the majority of your city into the mountain itself. It can be done, look at that Turkish underground villages from the 10th century BC. If it can be done in the bronze or iron age it certainly can be done with your tech level.

Answer 2

As the montain is about 6000m high there is no way any enemy beast can fly at that altitude. Tada, fight won, no man lost.

If you don't like that, wind. Have the magicians of the city constantly swirl the air around the walls or above the city.

If that's way to much force, anti-air-units are always problematic when shooting from the ground up, but high, well built towers with shooting holes combined with stone houses with spikes on the roofs will be hell for anyone flying low enough to drop into the city and anyone flying high won't be able to drop that far down.

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Another idea, stone houses, strong metal doors and little windows everywhere. Tunnels with strong doors between houses. Now even if a thousand man land inside the city, they can be easily slaughtered because they are still outside on the streets and can't get inside but can be shot at.