Six/en
From oxat wiki
(SIX) - Devil-themed smilies LIMITED
The Six power allows you to turn yellow smilies into devils. To make a devil smiley, add #six at the end of the smiley code and to make a devil smiley with no horns or tail, add #6.
Note: #6 does not have a red background. Therefore, you need the power Red to make the background red.