Xorvintaal + Planar Dragons = good deal?

[ksbsnowowl]

Planar Dragons, described in the Draconomicon, are true dragons that do not have spellcasting.

Xorvintaal is a template that can be added to any true dragon.  The largest detraction of this template (flavor aside) is that the dragon loses its spellcasting ability.  They also lose their spell resistance.

This seems like a really good combination, from a DM's perspective.  Especially if you just then give your dragon the Awaken Spell Resistance feat.

Is this a dirty combination to throw at one's players?  Is it a good idea?

[Kethrian]

Considering they get a greater benefit from the template, simply add additional CR to them to account for the fact that they are tougher.  I don't really know how much to add, but I'm sure you could eyeball it after a fight or two.

[nijineko]

is the spellcasting loss prerequisite?

[ksbsnowowl]

is the spellcasting loss prerequisite?

no. It just states that they lose the ability to cast.

“Xorvintaal dragon” is an acquired template that can be added to any young adult or older true dragon (referred to hereafter as the base dragon).

...[template abilities]...

Spells: Xorvintaal dragons lose the ability to cast spells.

[nijineko]

can't lose what you don't have, but on the other hand, if loss of spellcasting is not a prereq, then the template would simply prevent gaining spellcasting in the future, so long as the template is active/in force.

should be a go.