Apparently, it can be used to hatch the dragon egg to make another Ender Dragon spawn, no confirmed method on how to do this, or even if this is genuinely true has been posted.
You could always do (if you are using group manager) /manuaddv (username) suffix Example: &0&l[&b&lMod&0&l] then add his permissions individually by /manuaddp (username) (permission node). Make sure to have the prison ranks (a,b,c) as prefixes and are groups/sub-groups and do not conflict with suffixes.