Zija's introduction event can be triggered at Home if you pass a day with more than 20 (30?) characters available. You are given the option to either accept her offer, which will remove both her and a basic housing slot for 2 (Confirm?) days before another event triggers. Refusing her will open access to another Unique character. Both options will open a stabilized portal to her world, Grenea.
Upon entering her world for the first time, you will be greeted with another event that will introduce you to her sister, opening up the rest of her quest line, and granting the party +10 morale. Her quest line will involve 3 more unique events to complete.
The first event will trigger on Forest tiles, introduce you to the Elf Commander and give you some information about your objective, guiding you toward some orc camps to gather information about the lost artifact.
The second event triggers on Plains tiles where Zija will ask if you're ready to attack an orc camp. Choosing to fight will lead to a boss encounter with many orc enemies. Zija will bring along 3 goblin allies to help with this fight. Choosing to flee removes the event on the tile. This event does not always complete the first time.
The final event triggers on Forest tiles, bringing you back to the Elf Commander who will then suggest sneaking into the main orc camp to take their artifact back. Choosing to fight leads to a boss encounter with even more, larger enemies. Choosing to flee removes the event on the tile.
Once the final event has been completed, you will be granted the option to either return the artifact or steal it. Returning the artifact grants you Zija as a permanent unit, as well as the ControlGlove special recipe. Stealing the artifact give you recipe as well and a condensed crystal but Zija will notices and leave the party.