The Org/Rubel used Teresa's head which Clare carried with her and held up to Rubel, saying ~"Give me! Put inside my body! Teresa's flesh and blood!" Clare got her wish to be with "Teresa forever", lol.*
*Back before Teresa killed the bandits in that town, Teresa had left Clare in that town, thinking that a "human's life" was better for Clare. However, Clare disagreed, stripping naked in front of the townsfolk, and said this to Teresa: ~"I don't want nice clothes. I don't want nice shoes. I want to be with Teresa forever!". As I said, Clare got her wish, hehe.
Now, they didn't put Teresa's entire head into Clare, and there's no Teresa's face on Clare's stomach or chest. But, I wouldn't be surprised if they had implanted Teresa's brain into Clare. We do know that some part of flesh from Teresa's head was implanted into Clare turning her into an unique Claymore, being only 1/4 Yoma and 3/4 Human, instead of 2/4 Yoma and 2/4 Human like all other Claymores who are implanted with NY "flesh and blood".
Until the recent ch 110, all we knew was that "flesh and blood" was used for the implantation surgery.
However, the recent ch 110, suggests that indeed the brain is not needed for the implantation surgery and that any body part can be used, as Dae plans to use Priscilla's arm to make 3 uber AFs (NOT revived "Hokage Corpses" like in Naruto), and then the dead bodies of previous rank 1's, who hadn't Awakened, to make possible "Clare Clones", including Teresa's headless body itself, which also suggests that the brain isn't needed, but that any part of the body can be used.
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yes, the trainees with Clare were jealous of Clare having Teresa's flesh, and one of them thus challenged Clare to a sparring match. Where we see "Badass" Trainee Claymore Clare, and then again in her final test/trial, where she saves that same Trainee Claymore who had challenged her to that sparring match, as well as being successful, killing the NY, and becoming a ranked (official-active) Claymore.
Elena would become a ranked Claymore some time AFTER Clare. Both were extremely weak as Claymores and had to use a lot of yoki release to survive. However, Elena being a normal Claymore at 2/4 Human and 2/4 Yoma, couldn't resist the Awakening as she hit the 80% yoki release limit, as she needed to, in order to survive and kill NYs in her missions. Whereas, Clare being only 1/4 Yoma helped her to be able to resist Awakening better then Elena, and so it was Elena who had reached Awakening first. Clare would finally get pushed into Awakening, by Rubel sending her on a mission against a SNY, and also having poor Clare be on the pills as well... thankfully Raki was able to help motivate Clare into reducing her yoki release, and prevent her from Awakening. This also changed Clare into the prized Half Awaken, and this greatly enhanced Clare's Power level, as can be seen afterwards.
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Regeneration requires precise memory of the missing body part, in order to Regenerate back their CLAYMORE body part. Such a precise memory quickly fades, so they have a short time period (at most they have "Dauf's length of time needed to Regenerate") to Regenerate back their CLAYMORE body part.
Irene mentions that Claymores who can Regenerate, can Regenerate back HUMAN body parts as well, obviously being weaker than their CLAYMORE body parts.
However, we've never seen this, and it's possible that only Irene can actually do this, and not any Claymore who can Regenerate.
Rafaela CAN Regenerate, but it's been so long, she no longer has the precise memory of her eye, so it's forever lost. The reason Rafaela didn't Regenerate her eye when she still could have, is because she CHOSE NOT TO DO SO, as it was a reminder of her failure to save her sister and of her duty obligation to find a way to save her sister. The same is true of Clare's right arm, and Irene's left arm, while she was still alive of course. Also, the same is true with Galatea, as she too said that she can no longer Regenerate her eyes due to her not having the precise memory of them anymore.