The Candle of Neron is a special candle given to various people by the demon-lord known as Neron.
History
When lit, the candle will allow its holder to be granted their heart's desire - many wished for more power, some, like Lex Luthor, for vitality. The Joker just wanted a box of Cuban cigars. The downside is that in doing so, you forfeit your soul to Neron.
The candles do have a few interesting quirks to them. One of them is that the recipient doesn't have to be the one to light it, as Triumph learned all too well. Another is that some users seem to have lost their heart's desire over time, just as Mr. Freeze did. When Kid Devil lit the candle to grant himself super-powers, Neron made a deal with him that, if he did not lose faith in his hero Blue Devil, then he could keep the powers for free, losing his soul when he reached 18 if he did. Though Red Devil (as he was known from that time onward) did lose faith in Blue Devil as Neron knew that he would, it is unlikely that Neron gained his soul as he was stripped of his powers, then later killed.