Princess Ishtar's decision is quick. She has never seen Lyre made of glass before. In fact, she didn't even know it was possible to make them. Once in the palace however, she discovers that well, it isn't. The Lyre is completely silent, despite all her effort, she can get no sound out of it. Annoyed with herself for her foolish purchase, she puts it away, forgetting about it eventually.
As weeks pass by, Princess Ishtar continues to feel somewhat sickly. It's annoyingly persistent, perhaps she should do something different to get rid of it.
Princess Ishtar
A : Try to convince father to cancel the marriage
B : Observe rites at the Temples
C : Go for a Hunt
D : Observe the men in the barracks
E : Take a boat trip upriver
F : Take a boat trip downriver to the Kingdom of your probable future husband
G : Write-in suggestions
H : Go gloat at the prisoners
I : Visit the royal library
Nur-Skalen
Worryingly, it seems that the Amulet's drainage is continuing, even though it is not attaining any greater amount of internal power. A closer inspection of the amulet and it's surrounding reality reveals what is going on. Your intrusion; the amulet, is causing scabs to form over the wound in reality. They're slowly growing over everything you have affected, including not only the amulet but also Princess Ishtar herself. It is a slow process, very slow, but unless something is done it will kill her in time.
You know you have many ways to deal with it. One is to use brute application of force, using the lifeforce of others to power the amulet and wipe away the damage. Another is to execute rituals, pushing back reality and keeping the wound open. The last you know of is one you already knew about before, transforming the body so that it can be sustained of the trickle of magic leaking through.
A : Observe Princess Ishtar as she does her business, taking the opportunity to glean knowledge from everyone she meets
B : Aid Princess Ishtar in her doings, lending her your strength and intellect. Such action is draining however, and your powers in the mortal realm are very limited. !
C : Aid Princess Ishtar in her doings, by shoving a piece of knowledge into her mind. Such action is far less draining than others, but she may be distraught to suddenly speak another language, or to know about mythical beasts.
D : Manipulate Ishtar's actions : This will open up additional actions that further your demonic ideals, or can be done just because. Using them excessively may cause suspicion within Ishtar or others.
E : Communicate with Princess Ishtar. The Princess has no idea that you exist within this gem, while you can manipulate her actions, having a willing and informed accomplice makes things that much easier
F : (Long-Term) Manipulate the Princesses body to be more in tune with your demonic power. This would allow you to deploy your power, and the power of your amulet, more effectively through her as a conduit. It may have leave traces, but as long as you can focus correctly and do not need to interrupt the process to blast a bunch of energy through the carefully woven spells (option B/C), you should be fine.
Note : I'm not entirely certain if things are going okay. Bit lost with the limitations and benefits of the format.
Note 2: The Lyre is not useless, but it is one of the not immediately useful things you could have bought.