Back in the 1990's I borrowed a series from someone. The series was about elves and humans who transformed into elves. One specific character had lost a leg and when he transformed, his leg grew back. I would appreciate any help! Thank you for all the suggestions! Here is more that I can remember: The story was all set in modern times. There were 3 books in the series at the time I read them. The guy who was missing his leg was questioned by the authorities who did not think he was the correct person they were looking for because his leg had grown back. As elves, they did not need to sleep and were immortal.
Gael Baudino's Strand series. The book you're thinking of might be Strands of Sunlight. The series covers a span of centuries. In that book, which is in the current times in Denver, it has humans transforming into elves. They are guided in their transformation by Natil, the last of the true elves. TK, a Viet Nam veteran, who lost a leg, grows a new one as he transforms. The police question him about the bombing of a crack house, but since they're looking for someone who's missing a leg, they let him go.
From the Wikipedia summary:
After Heather, one of the Elves, is shot by drug dealers for TK's efforts at evicting the crack house from his neighborhood, he steals military ordnance and demolishes the crack house with two pounds of C4 after a desperate gun battle that destroys his artificial leg. Concluding his transformation into an Elf while he sleeps a few nights later, he wakes up the following day whole, his leg intact, having finally discharged his last tie to his old life. When the police come to question him about the pieces of his artificial leg, which he left at the ruins of the crack house when Sandy drove him to safety, the presence of both of his legs deflects their attention away from him.
Odd possibility, but you mention that it's a series. Are you possibly thinking of one of the Shadowrun books? I can't recall a leg regrowth scene in any of them, but I didn't read all of them. The Shadowrun universe does have people transform into various mythological creatures (elves, dwarves, trolls, orcs, to name a few) although the explanation is that mana which has returned to the world has reactivated what had been dubbed junk genes- so they're all homo sapiens (the same genotypes), but different phenotypes.
Could this be "Eldest" by Christopher Paolini (The second book in the Eragon series)?
The main character is suffering a severe spinal injury which is magically healed when he transforms into a sort of elf creature...
With trembling fingers, Eragon reached around the nape of his neck in search of his scar.
He felt nothing.
Eragon tore off his tunic and twisted in front of the mirror to examine his back. It was as smooth as it had been before the battle of Farthen Dûr. Tears sprang to Eragon’s eyes as he slid his hand over the place where Durza had maimed him. He knew that his back would never trouble him again.