Author's Note
A story idea I came up with while talking on a forum with other Ben 10 fans. I decided to take the first part from another one of my stories and go on from there.
Story Start
"LEAVE HIM ALONE!" A panic and desperate yell filled with utter desperation sounded out throughout the smoky area. She felt weak, her body sore and drained from having to disable the vast amount of serpent like creatures that were cased within armor. They had just kept coming like an endless infestation of ants and roaches and it took nearly all her energy to tear apart the massive horde. Though the other creatures, those armored warriors hunting the two of them like a wild animal was just as bad. The other one that Ben defeated activated some bomb whose energy affected the Omnitrix and the concussive force of the blast resulted in both Tennysons getting second degree burns and broken bones.

The creature though, with its long black dreadlocks and crablike face ignored her. It merely extended claw like blades from its armor as it prepared to kill her cousin. Gwen Tennyson had never felt so helpless. Her muscles felt like they were heavy like stone, stricken with weight that made her felt like she was buried under concrete. Pained coursed through her body, wounds worsening as a pink-magneta glow gathered at her finger tips and she hurled it at the creature. The weak burst collided with its back, causing the creature to stir slightly before dismissing her as not a threat.

She let out a cry as she fell down onto the ground after her attempt to stand. The horrible stench of deaths and alien bodies filled the air and pervade her mouth. If it wasn't for the fact she had only thrown up once earlier that day Gwen was sure she would lose whatever else was left in her stomach from that day. The creature seemed to be taking his time, some sort of sadistic glee as he tossed Ben to the side resulting in the pain waking him up.

''Ben! Run!'' Gwen cried out, her voice dry and raspy from the pain and lack of hydration as she tried to force herself to her feet, her arms trembling and sharp pains going up through her left leg to her spine. Ben, recovering tried to fight off the creature with his blaster. He wasn't going to leave her; she didn't know why she cautioned him to run. Stupid, goofy, simple, brave, kind-hearted, loyal Ben.

Tears stained her eyes as she laid, the sounds of Ben's cries of pain as the creatures metallic blades tore at his flesh. This one, it wasn't like the others. It didn't simply hunt and killed its prey like a hunter. It was sadistic; it liked toying with whatever it was after and to make them suffer.

The other crab like creatures didn't go after innocents or their allies. Gwen noted this when a pregnant woman was caught in the crossfire and they let her go or they waited until Ben transformed before attacking. But this one, it was the very definition of a monster. Like many murderers that preyed on people, women, children, or anyone that was perceived as weak the sort of monsters that Gwen took a solemn oath to fight against to protect innocent people.

Gwen was able to muster a bit of her power and fling it at the creature. It caused the creature to stumble and for him to narrowly avoid a shot from Ben's blaster. The creature turned his attention to her and fire at her with his wrist canon. It all happened so fast, a flash and then her body being thrown.

She quickly recovered and looked up, only to see Ben's still body appearing from a green flash. "No!" she yelled. "Ben?" Gwen cried as she went over to his body. "Ben! Please, get up!" He did not move. Her voice became strained and hoarse. "Ben! You can't leave us! The world needs you! Our family needs you! I need you! Please...don't...leave…me." Gwen begged, half sobbing and wailing.

This couldn't be happening. This couldn't be real. Despair washed through her, as tears dripped down her cheek. "Ben…" as much as she wanted to block out the realization, she knew she couldn't.

A sound of a chortle of whatever that creature was doing drew her attention. It drew out some hunting knife of some sorts.

At that moment something within her snapped. A sudden wave of rage swept over her, drowning out any and all matter of reason. Her compassion ceased and nothing but a cold hatred reflected in her eyes. Gwen floated to her feet as power like never before coursed through her. The tears continued to flow as hot energy coursed through her, a violet blaze reaching out. Slowly but surely her body began to change, the right part of her face began a metamorphosis. Blazing anger coursed through her as bit by bit she began to transform as the tears dripped down her cheeks.

Slowly but surely her Andotian heritage began to take hold, slowly dissipating her flesh and clothing. 'No more.'

The strength continued to flow through her body. 'What good is my power if I can't even protect those I care about most?' she angrily thought as hot tears seeped down her cheeks and dropped to the rocky landscape of the ground. 'I'll...I'll make him pay...' Gwen could feel her power steadily growing, that power surging to get free and she knew what would happen if it did. Bur right now she didn't care.

Before the alien could make a move, tendrils of pink manna captured him like vines and exploded around him with such force, he was thrown back across the landscape and into several trees. With speeds she didn't knew she was capable off she popped up next to him and began hammering him with a series of attacks.

Not for a single moment would she allow the creature to have a chance to fight back. This power was exhilarating; it made her feel powerful and so free. He couldn't stop her; nothing was going to stop her. She hammered the alien into the ground, paying no attention to the fact that her blasts were ripping apart his armor or the fact that the creature was heavily bleeding and defenseless. She wanted to make him suffer.

A horrendous wail escaped her lips as she summoned all the power in her body and cast it forth against the defenseless creature. The explosion of power shook the surrounding area, leaving nothing but a crater in its wake. When it was over Gwen returned to her human form as a result of having exhausted too much of power throughout the day's events to retain the form.

Gwen went back over to Ben's side. She cradled his form in her arms. The others would eventually show up, having picked up on the distress signal they activated, but it was too late. Ben Tennyson was gone, but the world still needed a hero. "Goodbye Ben. I love you." She would fight in his place, and keep everyone safe in his stead, just like how he would have wanted.
Chapter End
This isn't a oneshot. The story will continue, but not in a way any of you are going to guess.