Few years went by. When Eir, Thor and Loki got around the age of ten, their formal education started.
As god's lived for thousands of years, it was common for them to study for around a century minimum. Yeah it sounded kinda harsh but their education system was relaxed and idle. There was no compilation with other anyways so they could learn on their own pace.
As a god, they were expected to learn about the history of their ancestors and warriors of past and major events and wars.
They were also tought different cultures around the universe, different language of importance races.
Other then that they had to learn etiquettes and manners.
Martial arts and war tactics were also necessary.
Thor was good at martial arts compair to both Eir and Loki. His God blood and his affinity to thunder made him stronger and faster then other. Eir also had God blood so she was stronger then Loki physically but due to her priority being gathering knowledge she's wasn't good at fighting, well at least compair to her siblings. She was strong enough to beat a foot soldier at her age so she was ok with it.
As they were god, they had to go through some special tests to determine their domain. Every god could control an aspect of reality which they were attuned too from birth. Like Hela their secret sister had domain over death, Thor had domain over thunder. Likewise Eir was born with domain over life. She felt a different connection to every living creatures be it plants, insects or any other human.
She could heal their vitality and her own too. And those simple minded creatures like birds and animals were never afraid of her and always gathered around her when she was alone or make sound when she passed by as to greet her.
It was confirmed that her domain was over life which was quite look up by other. She was called Goddess of life. As Thor's domain was confirmed as Thunder and thus he was called God of thunder.
As for Loki, he wasn't originally a god, so he didn't have any natural affinity towards any domain. And because of that he always felt out of place. He coused quite the trouble for others and had innate talent for magic and illusion so he was illustrated as God of mischief.
Thor mostly preferred learning to fight and using weapons. Loki on the other hand picked up tricks from his magic instructors and mother to couse trouble.
As for Eir, she could be called the cool headed and mature child of the three siblings. But not responsible. She never shone intrest in politics or any important roles of their realm. She was only interested in gathering knowledge about this and that.
That was why she grew distant from other family members especially Thor and her father Odin. She was with her mother Frigga most of the time and occasionally she would see Loki their too. He even tried to pull some prank on her but as she was also the practisaner of the same field and more advanced on top of that, his tricks never worked on her. So Loki lost intrest in her too.
As Eir was constantly learning stuff from her instructors and her mother, she got good at asgardian magic. She could now perform healing, energy channeling, illusions and small scale space magic.
Like this, many years passed.
Eir was now basically a shut in. She was mostly at her research lab which she got permission to use after they were 20 years in their youth. As a goddess with domain over life, she had to understand her capabilities so she did quite many experiments.
Now she understood her innate ability more closely. Well basically she had the healing capabilities of any healer which could work on any thing that was biological but just amplified around a hundred fold. Other then that she could also drain life energy from others and kill them in seconds. It would be difficult with her opponent as a God as they had high vitality and resistance. But for a normal human facing her could be instant death if she wished so.
As for Thor and Loki, they were growing as in original timeline. Become of their sisters shut-in life, they were like basically two brothers completing against eachother.
In this manner, their hundred years of basic education finally conclude.