Combat in Goblin Keeper, is asynchronous. This means that, you will launch your attack, and the combat resolves on its own. It also means you don't need to wait in game, while your Creatures travel to the target, and back. You can log out, and log back in later, to see the results.
For attacks, the primary decisions you make will be which Creatures to send, and your target. It is possible to submit 5 round delays between Creatures. This will allow players to develop strategies on when to send Creatures into battle. This can be based on their speed, or possibly their roles in battle.
Defense consists of Dungeon layout, traps, Creatures and whether you decide to have your Creatures on guard, or not. Creatures that are not in the Dungeon, at the time, are not eligible to defend. There are many strategies and Dungeon setups.
Battle Playbacks are available for attacks on the two lowest Elven Settlements. When attacking another Overlord, you will receive a Playback, if you survive the attack. This will provide valuable intelligence on your target. You will be able to take away information on the layout, Traps, Mines, Creature types, the existence of Safe Storage, Room levels and more. If you are attacked, you will always receive a Battle Playback. The exception to this is in a Spy mission. There is a chance that you will not be informed, at all, when another player Spys you.
Each Creature has statistics. Health, Attack, Carry Capacity, type of Damage, Resistances, as well as their role in battle. These statistics can help players determine how to best utilize their troops in battle.
Combat occurs in rounds, with a maximum of 1800. The order the Creatures attack, is determined by their initiative. The Traps have initiative 0, this means they activate first, if they have targets in range. Movement, attack, and special abilities all have a certain number of Rounds that must pass in between uses. For instance, this means that a Creature with a Combat Speed of 1, will attack 3 times as often, as a Creature with a Combat Speed 3.