Independent Fire Elemental Arm "Graft"?

[Kavenoff]

Okay, so, I'm new here, but I have a question I thought I'd register to ask... with a bit of necessary backstory first.
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As a child, [Name] grew up in an isolated clan of demon hunters, located in a forest relatively near a forbidden volcano. The children of said clan trained in the forest from a young age, but had a sunset curfew, and were NEVER allowed near the volcano.

[Name] was a smart boy, and knew that if he revealed his ability to understand elementals, he would share the fate of his cursed brethren. (Magic was seen as forbidden within the clan, and anybody showing such traits was publicly executed, no matter the age). Unfortunately, while smart, [Name] was mischievous and sneaky... or maybe he was just mischievous.

[Name] snuck out one night, well past curfew, just hours before he would be allowed to take a test to become a full-fledged demon hunter. He cut through the forest, and headed up to the volcano, unaware of his being followed by a vengeful elder who had previously seen him communicating with a brazier.

[Name] found, right by the caldera, a flaming portal, which [Name] assumed to be to the Elemental Plane of Fire, and next to it, a Half-Fire Elemental Dire Dragon Turtle... not that he knew that.

(From here, to summarize, Dragon Turtle nearly kills [Name], who barely survives, having his right arm seared off at the shoulder; vengeful elder tries to finish off [Name], but gets hit and ALSO nearly killed by Dragon Turtle. [Name] manages to get up and tackle elder out of the way of Turtle finishing off Elder, risking dying himself.

Turtle is so impressed that he decides to BECOME [Name]'s right arm, and keeps his own consciousness in the process, as well as his capability to breathe steam and fire.

Elder takes [Name] back to the village, ashamed of his own actions. Elder arrives at noon, and, after much council debate, ends up voting for the exile of [Name] rather than execution. [Name] leaves to the city.)
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Now... my question is... HOW would this work? Is the turtle a graft? Is it something else? Gah... I'm confused on how to do this... but I want to make this character!!! I want it to be viable, but not broken at earlier levels... By the way, [Name] IS an Elf, and was planning on becoming a Sorcerer.

Thanks for help!

[Red Fel]

Well, there are rules for intelligent items (http://www.d20srd.org/srd/magicItems/intelligentItems.htm). I would simply apply those rules to a graft, add some fire flavor, consider the appropriate penalties for using the graft (if any), and call it a day.

Dragon Turtles are usually neutral, and Fire Elementals usually neutral, so chances are your graft will be similarly neutral. The sample Dragon Turtle has an Int of 12, so assuming your graft has a similar Int, I would give it Draconic, Aquan, and Common, but you could replace Aquan with Ignan. The sample DT also has 13 Wis and 12 Cha, so assuming the graft has the same, I would put its value on the Intelligent Item table at either the second or third slots (2,000 or 4,000 gp equivalent), which would grant it either empathy or speech plus two lesser powers.

It's up to you whether you'd give it a Dedicated Power/Dedicated Purpose.

Mind you, this is a pretty dad-gum potent item for a first-level character, and would likely eat up your WBL.

As an additional side note, Magic of Eberron contains specific rules for Elemental Grafts, including the Elemental Scion of Zilargo class, which is basically about forming a partnership with your elemental graft. You might consider the Hands of Flame graft from that book, which replaces your arms, activates as a swift action, and allows your melee and unarmed attacks to deal +1d6 fire damage and set things aflame (costs 4 HP). Simply tack on intelligent item features, put it on only one arm instead of both, and have a ball. (Note that, if you go with Elemental Scion, at ESZ level 2 your graft becomes intelligent anyway.)

[Sewercop]

Symbiotic template from savage species.
Find a way to mash it together without crippling your sorceror progression.