This is a one-shot story
After he had killed the Gyaos with his self-destruction ability Gamera is sent to a dimension.
Gamera woke up under water
"Where am I, I am...alive ?" Gamera asked to himself he knew he self destructed in an attempt to kill the Gyaos "Ughhh" Gamera then realized that he was still a bit injured.
He then senses a great and enormous heat coming from a mountain. He himself a creature being able to feed on fire retracts his legs and tail into his shell,shoots rocket jets,flies out of the lake and began to fly towards the mountain.
...
As Gamera headed close to the mountain...a Dragon suddenly bursted out of the mountain,took flight and headed streight for a small town.
Fearing that the dragon could be a potential threat,Gamera took action
"What have we done ?..." Bilbo asked in shock then he suddenly saw Gamera heading streight for Smaug
...
"I am fire...I am-" Smaug never got to finish as he turns to his right only to be shocked when Gamera grabs him by the neck takes him away from the town with force.
...
They both reach a forest and Gamera throws the dragon on the ground with force causing him to crash, before he himself landed to confront Smaug.
Smaug got up and angrily looked at Gamera
"You...You DARE interfere...DARE attack ME ?" Smaug said his tone was full with hatred
"Yes...I do...I cannot let you harm innocent souls" Gamera said with anger
Now Smaug was a bit more composed
"What manner of creature are you excatily ? You look like a turtle...though different" Smaug asked with anger and curiosity
"I am Gamera, I was created in Atlantis for the soul porpus to protect the innocent" Gamera answered
"That is interesting...do you know who I am ?" Smaug asked
"I do not and I do not care" Gamera responded irritating Smaug
"Do not get overconfident...you may be bigger...but you seem to be wounded" Smaug said
"This wound means nothing to me...I have felt much worse than this" Gamera responed
"Well...then I'm sure you've felt THIS !" Smaug said before unleashing a massive amount of fire on Gamera.
However thinking this was over the flames soon disappeared and Gamera appeared completely healed
"WHAT ?! What trickery is THIS ?!" Smaug asked in Anger and Shock
"Perhaps I should have said this earlier...I feed on fire" Gamera said
"WHAT !" Smaug asked in disbelief
"That is correct...fire in nothing but a food source to me like sheep are to humans. When I consume fire my wounds heal and my strength grows" Gamera answered
"NO ! That's a lie ! No creature on this Earth can do that !" Smaug yelled in extreme anger and disbelief
"Well...it would seem that 'that' is no longer true" Gamera said calmly
Out of extreme anger Smaug unleashed another wave of flames but like before Gamera absorbs it and grabs Smaug by the neck
"It's over" Gamera said before grabbing Smaug by the head and snaps his neck.
Gamera then returns to lake town carrying Smaug's body and drops it in the water.
"The dragon is dead,you may no longer fear him" Gamera said before flying away
Some of the people of Lake-Town began to cheer for him
Well that's all hope you guys enjoyed.