Skill Trees

Each time you kill an opposing player's troops in a battle, you receive contribution points. These are the stars you can see in a battle report.

Contribution points can be exchanged for skill points, at a rate of 1000 contribution for 1 skill point.

Gold and resources can also be exchanged for skill points, at various rates.

Gold exchanges at a rate of 2000:1, or you can select to exchange in bulk (10000:5 or 50000:25), but the rate is still the same - it's just quicker.

Resources can be exchanged, at various rates depending on the resource. Stone exchanges at 200:1 and copper ore exchanges at 1000:5, for example.

If the exchange rate ends up being better than the gold exchange rate, it is more economically beneficial to exchange the resource directly, and perhaps convert your gold into this resource by buying it in the market to exchange.

This happens most often with Stone and Copper ore, which can often be purchased for ~9 gold per load, at which price you can get skill points for 1800 gold, instead of the standard 2000.

Most other resources have an unfavorable exchange rate, and you'd be better off selling them to exchange the profits as gold and/or purchasing Stone or Copper Ore to exchange.

Once you have collected 500 skill points, you get a star.

If exchanging gold for skill points, it will cost 1000000 gold for each star. If you can purchase Stone or Copper Ore to exchange, it may cost you ~900000 gold worth of these resources. If exchanging any other resource (unless at a 2x or 5x rate), you will likely end up spending more than 1000000 gold worth of the resource.

If exchanging contribution (enemy player troops you've killed), it will cost you 500000 contribution points (the stars that show up on war reports, and which are reported to you in the email after each war you are involved in).

The star (or multiple stars) can then be used, along with a bunch of additional gold, to purchase skills that make your troops stronger. The star(s) are part of the purchase price of the skill, so you don't keep it/them after use.

To unlock more advanced skills within the same unit's tree, you have to complete the skills before it, but if it is a skill that allows you to upgrade it multiple times, you only have to upgrade it once to gain access to the skills beyond it.

Skill trees for stronger units are initially locked, and become unlocked when you've studied the specified number of skills. This is the number of skills, NOT the number of stars spent - if you learn a skill that costs 2 or more stars you still only get credit for learning 1 skill.

Note: the resource exchange rates for stone and copper ore are dependent on them being less than 10 gold/load in the market. If they are higher than that it is no longer beneficial. The opposite holds true for other resources - if their prices drop in the future they may offer an advantage over gold as well.