The Ice Dragon is a special unit in Stronghold Legends, and only available to players who are currently playing as the Ice faction.
They are recuited from The Ice Tower, costing 1000 gold and 250 honour. You can find out ways to generate Honour in the game here.
You can purchase an Ice Dragon at any point throughout the game, although you can only have one Dragon at any one time. Once it is killed, disbanded or lost, you can instantly recruit another one, assuming you have the required resources.
Unlike all other units in the game, Dragons take some time to recruit and you do not have access to them instantly. Once you have bought your Dragon, a purple egg icon will appear on the right side of your screen, with a red line slowly moving clockwise around the outside of it.
This process is preparing a Dragon egg, and you will not be able to hatch your egg until the line is completely red. Once the egg is ready, you will be able to see this either by noticing that the red line is complete, or by checking your Ice Tower, as a large blue egg will appear on the top of it when it is ready.
It is at this point that you may hatch the Dragon and use it in the game, at any time that is convenient to you. There are no time limits on when you can use your Dragon egg, and theoretically it could remain there all game until you need it. To hatch the egg, left click on the purple egg icon, which should instantly turn into a Dragon icon. This will also instantly spawn an Ice Dragon near the Ice Tower instead of the Dragon egg which was there previously.
Once activated, you have approximately 3 minutes to do as much damage as possible on the map using your Ice Dragon before the countdown has finished and your Dragon is removed from the map. Since Dragons are so powerful in the game, they are time-limited in order to prevent them from easily overwhelming players.
Whether or not you actually do any damage is irrelevant, because the timer begins as soon as you hatch your Dragon, and you can see it counting down counter-clockwise on the Dragon icon on the right of the screen.
The Ice Dragon can also be killed by enemy units or defences before the countdown is up. In this case, you will lose the remainder of your time and the Dragon will be removed from the map instantly. The Ice Dragon can attack almost any military unit in the game, and cause untold havoc on the map.
However, unlike the Green Dragon and Black Dragon, the Ice Dragon cannot attack buildings. Dragons are very durable and resistant to attack by almost any unit, except for attacks by Dragon Harpoons which can quickly deplete their health.
If you're attacking an enemy castle and it has stationed Dragon Harpoons on or around it, it's essential for your Dragon to take these out first in order to survive. Once the Harpoons have been destroyed, the Dragon can attack any enemy units as normal without the risk of quickly being killed. Dragon Harpoons can attack Dragons from a distance before they are in range to attack the Harpoon itself or anything else nearby, so it's important you minimise this damage.
It's important to know that unlike the other Dragons in the game, Ice Dragons cannot attack any other Dragons. If the enemy spawns a Green Dragon or Black Dragon of their own, your Ice Dragon can easily be attacked by it, but it cannot defend itself, even though it will try and you will technically still be able to give the order to attack the Dragon.
The Ice simply has no effect. If your Ice Dragon is attacked by another Ice Dragon, then it will take no damage, and your own Ice Dragon will also be unable to give out any damage to the enemy Ice Dragon as well.
While it cannot attack other Dragons however, it should be noted that Ice Dragons have the same attack strength as Green Dragons, meaning that it is stronger than the Black Dragon, although which Dragon is the weakest remains debatable because of these facts.
Unlike ground-based units, because the Ice Dragon is an aerial unit, it can fly through the air and therefore travel over water or other impassable parts of the map by land. You can use this to your advantage to significantly reduce the movement time of the Dragon, and to gain access to other areas which are difficult by land to take out crucial defence systems.
Please note that Ice Dragons, like all aerial units, are still susceptible to damage by fire on the ground. It's therefore best to keep your Dragon moving around and keep them out of fire areas to protect its health. If you're feeling lazy, you may even wish to attack an enemy Lord using an Ice Dragon.
An Ice Dragon can easily kill an enemy Lord within its time limit, and if you're struggling with your troops or defences then this is a potential option, although it is a relatively easy way to win a game and is not really recommended in practice.
Tip: Dragons are one of the supreme units in Stronghold Legends, and are virtually untouchable by all other units other than Dragon Harpoons. For this reason, you can cause immense damage to the enemy, particularly if you attack melee units on the ground with no nearby ranged units to attack you back.
For best effect, use your Dragon to quickly cause damage to an area and then move on to a different area before the enemy can mobilise their ranged troops or any defence. You can quickly destroy an enemy army by doing this.