Clary's POV
I woke up with a start due to seeing a rune that could turn any mortal, including mundanes that are connected to the shadow world, immortal. But there was a catch, you either would have to become half downworld or get different blood once immortal. I picked up my phone and called the gang hoping they all would come for a very important meeting which eventually happened so I didn't have to worry. "What was so important for a meeting at freaking five in the morning?!" Jace yelled. I rolled my eyes and glanced at Alec. "What?" Alec yawned. "This might interest you so you better listen," I said. He just looked at me like I was crazy before he started laughing which eventually caused everyone, including myself, to laugh as well. "I have a new rune!" I yelled during laughs making everyone stop. "What?" Simon asked, curiously. "Clary, what type of rune?" Izzy asked. "Immortality," I answered.
"Is it safe?"
"Yeah. It can work on mundanes connected to the shadow world as well. I experienced on my pet which worked so I'll say it's safe"
"Well, that's good"
"There's a catch though"
"There's always a catch on a new rune," Jace said rolling his eyes. "You'd either have to become half downworld or get different blood once immortal," I replied glancing at Alec who remained silent but looked interested as well as concerned or afraid. He knew what would he have to go through if he chooses to become immortal but at the same time would be able to  have eternity with his soulmate. Magnus looked interested of course since he has seen many of his past lovers die but at the same time would support Alec's decision. "We need to be alone for a moment," Magnus announced, breaking the silence. We all nodded and left the two lovebirds alone.

Magnus's POV
"Alec," I said. He looked up and smiled. "I want to do this, become immortal, I mean," Alec replied.
"Are you sure? You'd see your loved ones die"
"I know but I'll be able to be with you for eternity and I can't live my life without you. I'm sure"
"Alec, know I'll support your decision whether you choose to go along or not"
"I know but I love you"
I smiled before kissing him quickly.

Two days later

"Are you ready?" Clary asked. Alec nodded allowing her to start the process and I squeezed his hand so he wouldn't be able to feel the pain of the rune as much. "Give it 10 minutes. You'll faint and after some time, you'll wake up immortal," Clary said once done with applying the rune before Alec collapsed in my arms. I smiled at the thought of having him for eternity and started to become impatient waiting for him to wake up. After what seemed like forever but was only a few minutes, Alec opened his eyes with a start while I gave him some warlock blood which would cause him to have powers but would still considered be a shadowhunter. It was hard enough to convince the clave for permission to do this but once I told them I'd give some of my blood giving him powers making sure he'd still be a shadowhunter, they agreed. "Alec?" I asked. "I love you for eternity," Alec answered before kissing me softly and quickly. I snapped my fingers and we were in our bedroom. "As I love you for eternity," I whispered between kisses.