Shadowhunter's never did have long lives. They, more often than not, were killed heroically at an early age in battle. That was the way a shadowhunter would want to go out. They would want their death to have a purpose. Shadowhunter's want to die for something, and for many, it wasn't even something they feared.
Magnus knew this. After over 800 years of watching nephilim after nephilim be killed too soon in battle, Magnus knew this better than most. It was one of the reasons why he avoided becoming too close with shadowhunters. It always seemed like the second he got too invested in their lives, mortality stole them away from him.
And contrary to popular belief, each time didn't get easier. The first time it happened hurt just as much as the last, and the only thing that changed was Magnus' ability to hide his pain. Over the many years he's learned to hold it in, tricking not only others into thinking he's ok, but himself as well.
You would think that at a certain point it's easy to forget. It should be easy to forget people and events that took place hundreds of years in the past. He should be able to replace all the memories with new ones, better ones, ones that didn't carry so much heartache with them. However all Magnus could do was push the old memories to the back of his mind and make room for new ones. The old were always still there, whispering warnings that he ignored every time, and regretted ignoring every time as well.
Magnus was able to make it through so many deaths in his lifetime by knowing that he could find someone else. He'd be able to find someone either just like the one he lost, or better. He didn't care if it would weeks or months or even years to find them because he had all the time in the world to find someone that was worth spending his time with. Someone else who was worth the inevitable grief.
One thing that Magnus thought would help was to constantly remind himself that this wouldn't be the last person he felt so strongly for. He often had that thought at the front of his mind the second he met anyone he could potentially see himself liking more than others. It helped him remember that it was worth living even after they were gone.
This wasn't the case with Alec Lightwood, his sweet Alexander. The second Magnus saw him he was drawn in by his lovely combination of blue eyes and raven hair. His personality was what kept bringing Magnus back.
Alec was selfless, often never even considering himself in the case of helping and protecting others. He was strong willed, determined, and never backed down, all the components of a great shadowhunter.
But he was also reserved, so used to having to hide the way that he felt. Magnus loved to watch as one by one Alec's walls came down, and he was able to see Alexander the person rather than Alexander the shadowhunter. Alec was always so easily embarrassed, with even the slightest touch or comment from Magnus bringing a dark blush to his cheeks. Magnus found it endearing each and every time. At times, Alec even had a dry, sarcastic sense of humor, though it could never compare to that of his adoptive brother.
Magnus grew close to Alec's siblings and their loved ones, but not too attached. He and Jace often went off on insulting sprees with one another, though they both knew deep down that it was always in good spirit. He felt closest with Isabelle, who he had both serious conversations with as well as more lighthearted ones about fashion. Clary was the only child Magnus had ever been able to observe growing up, and he continued to do so gladly, enjoying her company as well. Simon, however, he did not learn too much about, but that's ok; he has all the time in the world to learn about him.
Though the one thing that made Magnus' relationship with Alec different than all of his past ones wasn't even completely based on who Alec was or whom he associated with. What made him different was the way Magnus thought while with him. Magnus could never bear to think about a life without Alec. Throughout their entire relationship, Magnus never told himself that once Alec was gone everything would be okay, because he knew it wasn't true. Magnus knew that even with the ability to live forever, there would never be a single person in the world that compared to Alec.
This mentality was the reason Magnus was so protective of Alec. Call him selfish, but he just couldn't let his one true lovebe taken from him too soon. He followed him in to every battle, and while Alec was too busy worrying about others, Magnus was too busy worrying about him. He'd do anything and use any amount of magic to lengthen Alec's life because when you're immortal, any limited amount of time spent with the one you love is far too short.
One particular battle, only 6 short years after the day Magnus laid eyes on the most beautiful man he'd ever met was one that haunted him everyday. It was most definitely the largest war he'd ever seen; it seemed as if every demon from Hell was in attendance, as well as every Downworlder and Shadowhunter to fight them off.
Magnus spent the entire time by Alec's side, letting nothing separate him from his lover. He knew that while he was doing everything to protect Alec, Alec was also doing the same for him. They watched each other's backs, killing anything that came too close. Without even having to say the words they communicated their love, knowing that in such a battle they could easily lose the chance to ever say them again.
As Magnus felt the magic draining from his body he didn't care for his own safety. As his limbs grew heavy in weakness and his powers lacked the punch, not once did he worry for himself. All he could think about was Alec. Get Alec somewhere safe. Take him and run away, take him and hide where he's never be found, where he'd never be in danger again.
Magnus had no time to do any of that before he heard the most heart shattering sound, a sound that would repeat over and over in his worst nightmares: Alec's scream. A scream that immediately caused Magnus' heart to drop into his stomach, a scream that let him know something was dreadfully wrong before he even turned around.
And when he did turn around every ounce of hope that he had in everything being okay was gone.
Right before his eyes Alec had collapsed to the floor while clutching his stomach, and suddenly Magnus' world stopped. If the battle was still going on, then he couldn't tell, because the only think he could focus on was Alec.
The most despair Magnus had ever felt was when he fell to his knees next to Alec, pressing his fingertips to his body only to see that nothing was happening. He felt the most self-hatred when he lifted his hands, willing himself to emit some sort of magic only to see a single spark of blue and then nothing. He never screamed as loud as he did for help and then out of frustration when none came.
Magnus never cried as hard as he did when he pulled Alec into his arms, sobbing his name over and over again. He cried as he placed desperate kisses all over Alec's face, pleading for him to be okay.
And when those blue, beautiful orbs just barely fluttered open, it took everything inside of Magnus to keep himself from falling apart even more. He took Alec's face gently into his hands, telling him over and over how sorry he was. He was sorry for not being able to save him, no matter how many times he had promised he would. He was sorry for allowing himself to use up all his magic when he knew he should have saved some just in case of this.
After Magnus' apologies, the only words he could form were ones of love. He poured his heart out to Alec, who was just barely holding on. Magnus knew that he would have never stopped talking if it weren't for the gentle finger placed on his lips.
He abruptly stopped and stared down in agony at Alec, who whispered his final words to Magnus. Though they were only four simple words, they meant so much more. They conveyed the love he had for Magnus. They showed how much Alec really understood what his death would do to Magnus. But more than anything they expressed fear in being replaced.
Don't forget about me.
The last words were as selfless as everything else Alec had done in his life. They didn't tell Magnus to never find someone else that could make him happy. They didn't tell him that he is obligated to remain in touch with his family members. They simply asked that Magnus would always remember him and the love and memories they shared.
Don't forget about me.
The moment Alec finished the last word his eyes closed again, and with his last breath his body went limp. Magnus let out a choked sob and clutched the lifeless body close to his own. He shook with heavy sobs once again as he repeated his own set of words.
Never. I'll never forget you. I love you, Alexander. I'll always love you.
When the battle was finally over, Jace, who had already felt what had happened, along with Isabelle found him in the same position, and together they cried. They cried for the loss of a brother, a best friend, and a soul mate.
As this generation grew old and passed, Magnus was left to grieve alone. He suffered through an eternity of heartache, never again finding someone that brought him happiness, to ensure one thing: Alexander Gideon Lightwood would never be forgotten.