With your character's level increasing step by step, your talismans & assist talisman need improvement in their own level to be more powerful and give you more help.
Enhance is how this is done.
How to Enhance?
The Enhance icon can be found as one of the default shortcut keys.
If you remove it from the toolbar, it can be found in Character interface. Press C and choose Act to find it.
Characters can enhance their own talismans at any moment and any place as long as they are not in fighting status.
Talisman level should be matched with character's level to have the greatest powers. Weapon talisman can be enhanced after each increase in the character's level, while assist talismans need to be enhanced every 2 or 3 levels.
Open your Item Box and drag the icon of the talisman to the center of the enhance interface. Press "Start". You can choose Stop anytime during the process. Mobs can attack while you are enhancing, so you should choose a safe time and place.
Enhance mainly consumes character's Energy, which can be accumulated through killing mobs and rewards for quests. The higher the level of talisman, the more the energy needed.