Dread necro. Would it be a bad idea to dual class, on level 9 to wearer of purple?

[Sergio]

http://www.realmshelps.net/charbuild/classes/prestige/realms/wearerpurple.shtml

That's the class.

[noob]

In which way do you gain anything over taking levels in dread necromancer?
Yes you keep raising caster level at the same pace but you stop progressing your rebuke undead and you add less bonus spells to your spell list(this guide (http://www.giantitp.com/forums/showthread.php?214212-Reanimated-Dread-Necromancer-Handbook)have a cool list of spells to add to your spell list) and also you can not cast domain spells with a dread necromancer because getting a domain do not add its spells to your spell list(unless you convinced the gm otherwise).
Now there is other prcs that can give cool stuff you might pick up.
And if you really want to add the spells of a domain to your spell list you can just take arcane disciple.(and you do not need to have the domain for that) and another cool feat to add spells to your spell list is mother cyst.

[Grod_The_Giant]

It doesn't seem like it's offering you much. A few domain powers, a pair of the weaker item creation feats, eventually a paralyzing touch? What caught your interest about it?

[Silva Stormrage]

Also remember that Dread Necromancer's Undead Mastery's undead limit is based on CLASS level not caster level so you would be limiting how much undead you can control.