I played a lot before figuring things out in shadow lords:
The goal is to fight Gargos... but to achieve this you must take some of his powers from him or he will be very strong.
The mode is turn based, at every turn, you can use items, craft items, heal your fighters and complete some missions. Those missions consist of taking down "mimics" which are clone of the KI roster made by Gargos to conquer earth. You can take three fighters in your team. There's also some side quests and some story related quests with real KI characters involved.
If you succeed a mission, the corruption level of the continent where the battle takes place goes down, retarding the arrival of Gargos.
When a corruption gauge goes above a certain point, an Omen comes, if you take him down, Gargos lose one of his abilities, if you lose, he keeps it and will be stronger in the boss fight.
You can take down three of Gargos abilities, he will always keep some.
The thing is you want to fight Gargos but you need to make him weak enough, so you'll have to fight those Omen when they come, but you do not want them to come at the same turn because they can be tough to beat.
You often have between 3 or 5 missions each turn and can only use each of your fighters once a turn, you can also use two fighters for one mission (the ones where you get to fight multiple mimics for example) and when the mission is over your lifebar doesn't refiil, you have to use items to get life back or use healing items that works 3 turns and gives you life back at the end of a turn (if your character dies, you have to resurect him) thus making you choose some missions over others and so the ones you don't do make the corruption gauge level up in a certain continent.
So basically, you need to fight three Omens, each one of them will come when a continent gets corrupted enough by the Shadow Lord, but you'll have to make sure they don't come at the same time or too close to each other because you may want to make sur you have the right item to fight properly, which may take you some turns to get, or use your main against them, to be sure you'll win the fight.
When three Omen are defeated, just let the corruption go up in every continent and Gargos will come.
Stronger or weaker depending on you.
You get only one try against him with you three characters.
You get to unlock all kinds of documents about the background of the game, you can unlock the mimic skins for each character involved, and there is a "story" if you follow the good missions with the good characters.
I think it's really well done for what it is. But it's clearly not what people might expect from a fighting game, still, i like it. There's a good challenge and a good replay value, i don't care for the unlockables personally but it's a nice addition.
I would have liked a stage for every character, danger moves and ultimates but it's okay.