Underworld / Blade coast / Thorn king
Those 3 events may appear from time to time, and are very similar to each other in the way you play them. They will run approximately 7 days. You can gain some prizes and hundreds of rubies along the way. Usually there are "towers" that you have to attack one after the other, to reach the last target (in Underworld is is called: "cave castle"). You will have "resource lair" (in Blade coast they are called "pirates") which will give you resources, but the path to the end should only go through the "towers". You will have some "bridges" to repair (with resources) on your way through the last target.
Enter the event
I do not recommend you to enter the event if you below level 40, don't have all your "Barracks" at level 5 or aren't willing to lose thousands of coins and hundreds of troops for the event.
You decided to go into the event ? keep reading...
At the beginning, you will have to enter the event, with resources you pay. You will always have 3 options for your "camp": simple, more advanced/equipped and strong one. For the 1st and 2nd options you pay with resources (wood/stone/coins) from your main castle, for the 3rd you pay with rubies. For non ruby players, I recommend choosing the middle option.
Smart play those events
1. The first time you transfer troops to the camp, transfer tool with them too (ladders, rams and mantelets), so you can start attacking (if your capacity is full, you will NOT be able to transfer tools without troops).
2. Start to attack the first tower (and "resource lairs" / "resource villages" / "pirate ships" nearby), for level 1,2 you do not need tools. Keep your attacks and continue building "tents" to hold more troops. Do not build more than 1/3 of space with "tents", since you will need the extra space for decoration. Many people do a mistake building too many "tents" and does not have enough space for "drill ground". This is very bad, since with low "morale" you will unable to finish the event ("tents" can not be demolished)..
3. When you have resources, build some "supply storehouse" to hold more resources, and transfer from other kingdoms more resources if you do not loot too many.
4. Start building decoration to increase your "morale" — read later on about "morale".
5. When you keep your progress, expand the camp to maximum, and build more "tents". Always keep an eye on the "morale" value. If it goes down (when "tents" are built) build more "drill ground" items to increase it again
5. Within the event you will have some quests. Follow them (and complete) to gain prizes.
Morale is the KEY for sucsess in those events. Since you can not use any of your commanders on those events (you basicly attacking without a commander) your soldiers power on attacks rely on the level of your "morale". For example: If you use "crossbowman of the kingsguard" range soldier, the base range power is 121. If your "morale" is only 50% this soldier will have only 60 range power (!) This is why you will to increase your "morale" at the early stages of tthe event. You will need to build many "drill ground" items, to get a higher "morale" ratio. If you want to minimize your losses and have effictive attacks also on later (more powerful) targets, you will need to aim for a ratio of 150-180% (!).
Some of the events (when finished) has a "master level". When you click on "leave event" button which will send the soldiers + tools back to your main castle. At this time, you will have an offer to enter the "master level". This is an extremely hard level to finish, and might cost you tens of thousands of rubies. This is only for massive ruby players.