The Tartartos demons arrive at the battlefield with their eyes set on Lucy but an unlikely foe came to her aid, what is Accnologia planning? Are you ready for a rematch between spirit and demon, for another aid will soon arrive. 

~Lucy POV~

"Acnologia!", I yell on guard. 

"Calm down human girl, you have no need to be frightened", he says.

"Why are you helping me?", I ask. 

"You are the key to get us home to Earthland, that is all", he says.

"I'm the key?", I say.

I then flashback to Leo's words. Does this have something to do with the celestial Spirit King's words? 

~~"You are to aid the celestial wizard's Lucy and Yukino, you will do everything in your power to make sure you protect those two for this is your final battle", said the Celestial Spirit King.~

Whatever it is, I had a bad feeling.... My body then started to burn from the inside as I fall to the ground in pain. What is this intense heat? I then sensed Venus's magic power as she trapped both of us in a magic barrier.

"What are you doing!", yelled Acnologia as he tried breaking the barrier but failed. 

...

"What are you planning!", I yell on guard.

She then grabbed my head as she started whispering, her body was burnt and she could barely walk. 

~I VENUS, GODDESS OF THE FIRE PLANET, HAS CHOSEN EARTH LAND MAGE, LUCY HEARTFILIA AS MY SUCCESSOR!", said Venus as she smiled and fell to the floor. 

The barrier then disappeared as I felt this intense burning in my stomach, it was like every inch of my blood was on fire.

"You were the one who defeated Venus?", asked Acnologia. 

"Yes", I say to him. 

"Seems like you're in pain, my curse of pain would work wonders for you then", yelled Kyouka as she attacked.

Acnologia then interviened as E.N.D blew him away with one fist.

Kyouka then charged straight towards me as a barrier appeared. It was a barrier of fire. What's going on?

"She passed her power on to you", said Acnologia. 

"What does that mean?", I ask. 

"There's a secret to the god and goddesses of the planets and when you defeat any of the 8 deities guarding the planets, you take their place as guardian, it's one of Ankhseram's law, so if any one of you earthland wizards deliver the final blow to the planet guardians, you will take their place, you Lucy Heartfilia are now the Goddess of the Fire Planet, Venus", explained Acnologia. 

"No way, does this mean I can't leave?", I ask.

"I'm afraid so, the law of the cosmos is absolute", said Acnologia. 

.....

"Too much talking", yelled END as he attacked us both.

He was able to break my fire barrier with ease. 

"You should know fire doesn't work against me Lucy", said END as he punched me. 

"Natsu, stop it, this is not you!", I yell.

"You don't know who I am", he said gritting his teeth.

A water wave then came out of nowhere and washed him away.

"Aquarius", I say as Aquarius joined the fight. 

"Lucy, your FAIRY TAIL emblem", she said as she attacked the demons.

Her water washed them all away. I then look at the emblem on my hand. It's faded.

"What happened to my emblem, it's fading away!", I say.

"We were all just briefed by the Spirit King and due to the law of the Cosmo's, you're now trapped here forever, you cannot return to the human world, in about 20 minutes, your emblem will disappear too", said Aquarius with tears in her eyes. 

~Evaporate~ yelled END as his fire evaporated Aquarius's water.

"What are you saying?", I yell as a tear fell out of my eye. 

"We're saying", said Leo as he appeared and knocked END away. 

"This is", said Virgo as she attacked Kyouka.

"The last time", said Aries as she attacked Sayla.

"You're ever", said Gemini as they attack Keyes.

"Going", said Taurus as he attacked Marde Geer.

"To summon", said Cancer.

"Us", said Capricorn. 

"What are you saying?", I yell.

"This is our", said Scorpio as he appeared. 

"Goodbye", said Saggitarius. 

The world then stopped for a brief moment, I could believe what I was hearing, Plue, Lyra, Crux, Pyxis, and Holorogium then appeared. 

"It was an honor serving you", said Lyra.

"No No No No No! I do not want this!", I say screaming. 

As Acnologia and the spirits fight the demons, I stand there in pure shock as tears fall from my eyes, this can't be happening, this isn't true. 

Marde Geer knocked Leo away as he ran straight towards me. 

~Curse of Thorns~ he yells as a flurry of thorns flew straight towards me. 

A bright light then appeared in front of me as the thorns disappeared. Marde Geer gritted his teeth as the others fought. 

"We meet again, Underworld King", he said he appeared. 

"Celestial Spirit King", I say in shock. 

A key then appeared in my hands, it was a platinum key, was this the Spirit King's Key? 

"I thought you didn't have a psychical key!", I ask. 

"I made this just for you, FAIRY HEART will only be useful to you with the fairy tail emblem but it's disappearing, we have 15 minutes left to defeat the enemy. My key, you know what to do with it", he yelled as he attacked Marde Geer. 

"Thank you guys", I say as I rise to my feet.

~Star Dress: Celestial Spirit King form~ I yell.

To be continued in chapter 22: A Sky Full of Diamonds.