Source: Tome of Magic
Your personal truename is so charged with magic power that those who fail to speak it properly are warped by reality run amok.
Prerequisite: Obscure Personal Truename, 15 Hit Dice.
Benefit: Whenever a creature fails by 5 points or more in an attempt to speak your personal truename, it immediately takes 1d6 points of damage for every Hit Die you have.
Normal: The consequence for failing a Truespeak check to say someone's personal truename is that the utterance, truename spell, or other ability fails as well.