The Candle of Neron is a special candle given to various people by the being known as Neron. 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. Joker just wanted a box of Cuban cigars. The downside is 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 that power over time, just as Mr. Freeze. When Kid Devil used the candle to grant himself powers, Neron made a deal with him that if he didn't 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 he did lose faith in Blue Devil as believed, it's unlikely Neron gained his soul as he was stripped of his powers, then later killed.
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