Summary. When they were children, still innocent and small, Loki made Thor a promise. It was foolish of Thor to still believe it to be true. Five and one-Five times Loki was at Thor's side and one he wasn't.
"I promise I'll never leave you." Loki laughed as their mother guided them to the Hall of Healing.
It was routine, their mother brought them here once a year whether they were ill or not and Thor always hated it.
It was not that he was afraid, that was ridiculous, he was a son of Odin, he feared nothing just as Loki did not, always excited, ready to learn a new healing spell and yet Loki's promise settled something inside him and Thor reminded himself that he'd not been afraid.
"This is madness, Thor!" Loki cried as he walked with Thor.
"Then you will not come?" Thor asked raising an eyebrow.
Loki frowned, "I'll not leave you, brother, but I do not think going to Jotunheim is wise."
"Come, let us kill some Frost Giants." Thor cried out loudly, lifting his hammer, ignoring Loki's advice.
'You know I will follow where you go, Thor.' Loki thought as he left his cell, one step behind his brother, as always, 'Even to my death.'
Loki knew that the little ship Thor had taken would not be large enough if they needed to evacuate their people without the use of the Bi-frost and it was likely that Hel would destroy it, it is what Loki would do if he had wanted to harm their people.
So, Loki followed after Thor.
Loki's eyes locked on Thor's single one as he felt Thanos' grip tighten. He wondered if Thor could read the apology in them and as his spine snapped Loki wondered if this was where he'd always meant to be, dying for Thor.
They had won. Thor could see people rejoicing all across the field, could see Stark holding a young boy and Captain Rogers with his arm around his lover and so many others.
"Come back, Loki, I will not be angry at you for leaving my side, for breaking your promise. I will not even hold anger at you for faking your death yet again." Thor promised in the fading light, "Just... please, come back, please."
Thor covered his face with his hand as he began to cry, letting Stormbreaker fall to the ground next to him.
"Brother, please." Thor begged into the night.
But Loki did not appear.
Gods, I haven't done a five and one in years. I hope it was alright. I know the end was sad and I'm sorry.
I'll try to do a fluff piece for this fandom soon but I can't guarantee that.