Plot: Cas's borrowed grace was burning out and he needs more but you are an angel when Cas borrows your grace
Sippy Cup-Melanie Martinez
Your POV
"Castiel," I said poofing into the bunker with Castiel looking horrible. "(Y/n)," he smiled as he hugged me and I hugged him back. "Why are you here?" He grinned and I felt his emotions, human emotions. "I felt you borrowed grace Castiel, it's burning out. I want to help," I said as his eyebrows furrowed. "No (y/n). I am fine. Plus, I don't want one of our sisters or brothers to get hurt again," he frowned. "They're not Castiel. I am here to help you," I grinned and he looked at me as if he knows what's happening next. "No," his voice filled with worry. "Castiel, yes. I will. They need a leader and you're one. Yes, I may be a Grigori that still works for angels but that doesn't matter. Borrow my grace Castiel. It will make you stronger for a little while longer," I said touching his cheek then his shoulder. "I will not take your offer (y/n)," he said backing away with sad eyes. I squinted at him and walked around the bunker and grabbed a special container. I held it up and grabbed a silver dagger. "(Y/n) NO!" Castiel screamed but I held the dagger on my neck and slashed it a little as I felt my grace drain out and into the tiny bottle. Then in a few seconds, I felt empty and weak. I capped the bottle which has a blue mist inside it. Thrn I held my slightly bleeding neck and gave the bottle to Castiel. "No," he sternly said. I grabbed his hand and brushed it over my wound and it was gone. "Castiel," I returned sternly. I grabbed his cheek and pressed his lips to mine and snaked my hand to the bottle. I held the bottle next to our lips and I pulled away and Cas sucked in my grace. I sighed and turned away sheilding my eyes as Cas glowed light blue and the books from the library flew everywhere. Then the light died down and Cas was looking at me with worried bright blue glowing eyes. "(Y/n), I am so sorry," he pleaded. "It's okay Castiel I trust you with my grace. Please snap me to my vessel's house," I frowned. "Thank you (y/n). I promise to return your grace to you," he kissed my forehead and when I opened my eyes, I'm where I first saw everything.