Aptitude is a special resource that allows you to gain additional XP. Every day characters accumulate some based on their level. You can see the amount you will accumulate at your current level and the amount of XP for 1 aptitude point by pressing the aptitude button in the character window.
You spend aptitude automatically when your character does any actions that give them experience. You can see the amount of the resource that your character has left in the round reservoir located in your character window. The volume of the reservoir is limited, but once it fills, you will not lose the extra aptitude, instead of losing it, a dedicated NPC (Mora Zin) will save it all up for you. You can find her in Sulan (5509; -1985; 9) and in Sidus Ur (2162; 1242; 104) or just use the Restore button in the Aptitude window: the game will automatically send your character to the closest NPC.
Please note that if your character’s round aptitude reservoir is not full, Mora Zin will not accumulate resources. You can buy the extra concentrate from this girl and even receive some resource for free each day! If you would like to receive the rest of the aptitude points over the daily limit, you can pay for extra with Ausgyth Points. The aptitude you buy will be transferred to a special flask on the Aptitude window. In order to use the resource from the flask, just press the receive button.
This mechanic was devised so that the players who are unable to be online for some reason or just don’t have the time to spend on the game do not miss out on the daily aptitude, so it will not waste that useful resource. If you are an active player, then the aptitude will allow you to receive additional XP within the daily limit; you will not have to buy any from NPCs.