"Suit Yourself"
" My nindo? I do not possess a strong motivation, like the Konoha ninja. Nevertheless, there are people who I would not hesitate to vanquish from this world. Kiri-nin, to be precise. They once took everything from me. I know fully well that Fire Release is weak to the Water Release, the element the kiri-nin are proficient in. But could you just imagine the humiliation, when someone kills a Kiri-nin using the Fire element? That's my main goal, from this training. Like I said, Fire is chaotic, which is exactly what I shall use it for."
Saying this, Deathstroke placed his gloved palm slightly above the fire, swirling his hand about in an unpredictable fashion. The erratic movement of the flame could also be perceived as a reflection of the hand movements. He looked up, and spoke again.
"It makes me feel alive. This burning sensation reminds me of what it is to be human, it keeps me fresh. Well, as anyone would expect, it feels ..hot. But unlike some, who fear this fire, I love it. This warm feeling keeps my will burning. Heh, I almost sound like a Konoha-nin.."
As he heard the sensei's request to mold Katon chakra, he then proceeded to close his eyes. Knowing the feeling of fire, he knew that vibrations cause heat. He then concentrated in the chakra in his stomach, and started vibrating it vigorously. He could feel the chakra getting heated up, a bit too much, at one point. Nevertheless, he had an affinity for pain, and was able to mold this chakra without a hiccup.
"Well, that was different. It has a different tinge to it, when the fire is inside your body, instead of outside. The burning sensation, is quite unique. Hell, if I manage to heat the chakra to a point where it hurts alot, I could use this to escape a Genjutsu. Nevertheless, this feeling has alot in common with the fire I created. They both give warmth, and this feeling is unlike any other chakra i have molded before. That's as far as I can be detailed about this experience. There is more to it, but I can't just put a handle on how to describe it.."
"As far as I know, Shape manipulation has to do with the physical form on your chakra. For example, changing the size, the quantity of your chakra, its movement and range, all theses could possibly come under Shape Manipulation. I know for sure, that the 4th Hokage's Rasengan is a Shape Manipulation."
"Nature Manipulation is a bit more complicated, it is a high form of chakra control. It has to do with concentrating your chakra into one specific type of chakra, may it be Fire, Wind or else. There is also specific chakra paper, which has different reactions to different affinities. Here is what i know:
Katon - The Paper will Burn
Suiton - Not really sure
Doton - The paper will crumble into dirt
Fuuton - The paper will split in 2
Raiton - The paper will wrinkle.
Now, there are also advanced elements, caused by the fusion of two elements. For example, like you stated, Lava Release, and Dark Release. There are far more, But the only ones related to Fire are the aforementioned ones and Scorch, Dust and Boil as far as I know.
There is also the Yin-Yang release. Yin is the spiritual energy, while yang is the physical energy, That's as far as my knowledge on them goes."
"Now, to create a new technique, we need both Shape and Nature Transformation. Shape changes the form of the chakra, while Nature changes its properties and characteristics. So with this, you can use it to create an elemental jutsu, and then alter its appearance, into, say, a ball or a sword. This would be the combination of both theses transformations, in terms of ninjutsu."