Thanks Tinteanh!
Skills are not directly categorized by Elements like water, electricity etc. But we have Dark, Light and Balance as setting for our three Adventurers. Combos don't chain based on their element. They chain based on their condition effect. For example can a skill which require a stunned target connect to all skills that can set enemies to a stunned condition. This way we are not bound by the setting of the element rather than the mechanic of the ability.
We do have something like hidden and ultimate abilities. It is not introduced yet but to say in a short sentence: There will be Ascent Abilities. When you cast enough, let's say, dark abilities than you will gain an Dark Orb. This orb can than used to cast a finishing move which can turn around a fight!
We are looking forward for you playing the demo!
Edit: This is not true anymore. There will be interactions between elements. Some Elemental effects will affect other elements. Like water and lightning. The next update will have much more of these effects. Thanks for your input!