Here's your scene rewritten in much simpler language, while keeping the same dark, serious tone and key details. The sentences are shorter and clearer, so it flows more easily without losing the emotion or power:
Thunder crashed above us. Bright lightning lit up the night sky. Trees bent and shook in the strong wind. Their branches groaned. Rain fell in heavy sheets, turning the ground to thick, slippery mud.
The storm raged through the forest.
Every living thing had run to hide.
Except us.
I walked straight through the storm. The wind hit my chest like a wall, but I didn't slow down. The rain soaked me from head to toe, but I didn't feel cold. My body no longer cared about things like that.
Serah walked beside me.
She was the elf girl I had saved from bandits. She had given her life to me. Now she was mine, bound by contract.
My first follower.
She tried to keep up, but the storm made it hard. Her bare feet slipped in the mud. Her soaked cloak stuck to her like glue. Her silver hair was flat against her face. Still, she said nothing.
Good.
If she wanted to serve me, she had to be stronger. She had to survive pain and fear. The weak have no place beside me.
I didn't speak. She didn't either. She walked just behind me, head down.
Then I heard her sniffle.
She was trying. But she was still mortal. Still fragile.
We walked until the forest began to thin. The trees opened up, but the storm didn't stop. The wind howled louder. The rain kept falling.
I stopped.
She bumped into me and looked up.
"Let's find shelter," I said.
Her face lit up. She looked so relieved.
But I didn't care about her comfort. I cared only about her use. If she died from the cold, that would be a waste.
I let power rise in me. My eyes glowed red. My vision sharpened, cutting through the rain.
Then I saw it.
A barn, not too far away. Old. Worn down. But it would do.
"Follow me," I said, my voice cold.
She followed without question.
We crossed a field, and I pushed the barn door open just enough to peek inside.
Something didn't feel right.
It was dark. Empty. No animals. No noise.
Still, I stepped inside. Serah followed.
"Sit," I told her.
She sat on the ground at once.
"Flames of hell," I whispered, "give me your warmth."
A red flash lit up the barn. A ball of fire appeared above us, floating and glowing.
Serah took off her wet cloak and wrung it out. Then she squeezed the water from her hair. Her wet shirt clung to her body, showing her figure clearly.
She was beautiful.
But I didn't care about beauty.
Something else caught my eye.
Black marks ran from her stomach to her neck. Long, twisted lines.
"What's that?" I asked, curious.
She froze.
"Nothing," she said quickly. She reached for her coat.
But I was already in front of her.
In a blink, I crossed the space and grabbed her coat. I pulled her into my arms.
She tensed as I held her tight. I tilted her head, staring at the marks.
A curse.
"What did this to you?" I asked.
She tried to pull away, but I didn't let her go.
After a moment, she stopped struggling. Tears filled her eyes.
"Why do you care?" she whispered, voice shaking with anger. "Does it really matter to you?"
She was right.
It didn't matter.
But I didn't want her dying from something I didn't understand.
"No," I said. "But I won't let what's mine die."
I bent her head to the side. Her neck was pale and cold.
I bit my arm hard, until blood came out.
"Stay still," I ordered.
A drop of my blood fell on her neck.
It hit her skin and sizzled like fire on oil.
She screamed.
Her face twisted in pain. She fought to get free, but I held her tighter. Her chest pressed against me.
"It burns!" she cried. "It burns!"
I didn't care.
The black lines on her skin started to fade. Slowly, they disappeared. My blood was burning the curse away.
Her cries became weaker. Then her body went still.
She passed out.
Her breathing was slow and calm.
I let her go.
She dropped to the floor. I covered her with her coat.
Not because I cared.
Just so she wouldn't freeze.
I sat by the fire and watched the flames.
I felt nothing. No guilt. No pity. No warmth.
She was just another piece on the board.
And for now, I wanted her alive.
Then I heard something.
A low growl.
I looked up.
A creature hung from the barn ceiling. I hadn't seen it before. It had hidden well. Its dead, cold eyes stared at me. Its skin was burned and cracked. Its sharp teeth glowed with red light. Drool dripped from its mouth.
It dropped down, attacking me.
I moved aside quickly. The beast landed and let out a savage growl, like a wild dog. Drool flew from its mouth.
I wasn't afraid.
It looked like a stray dog to me.
It ran at me again, faster this time.
Still not fast enough.
I stepped to the left and swung my arm. My fist smashed into its stomach. The creature howled and flew upward—crashing through the barn roof.
Wood and metal rained down from the hole. I rushed to Serah and shielded her with my body.
Not out of care.
Just to keep her alive.
I stood and brushed myself off. No injuries. I looked at Serah. Still fast asleep.
I picked her up and laid her gently on a soft pile of hay.
Then I heard the beast again.
It howled. Loud and angry. Its feet shook the ground as it charged.
The growl it let out was deep. Savage.
I turned to face it. I didn't move. I stood still, waiting.
As it rushed toward me again—
I smiled.