Born of Three Thunders interaction question.

[TheChuck]

I have a player who wants to take Born of Three Thunders and the Force-Charged Energy sorcerer substitution level from the Planar handbook.  If he applied BoTT to a Lightning Bolt, would it then do 1/2 force, 1/4 sonic and 1/4 electricity? 

It would be easier on me to just say that he could not apply Force-Charged Energy to any spell that he had prepared with BoTT, but I don't think that's how the rules were meant to interact.

Of course, now that I've typed this up and thought it through more thoroughly I think I've answered it, but I want to hear what you all have to say anyway.

[StreamOfTheSky]

Just want to point out that BotTT is unique, it may be a metamagic feat, but you don't have to prepare it in advance:

"When you cast a spell with either the electricity descriptor or the sonic descriptor that deals hit point damage, you can declare that spell to be a spell of the three thunders, with half its damage dealt as electricity damage and half dealt as sonic damage."

As for your actual question I have no idea.  Probably what you said, either 1/2, 1/4, 1/4, or the two can't interact.

[X-Codes]

They're both optional, so the player can either choose to leave his spells normal, make them 1/2 normal, 1/2 Force (applying only Force-Charged), make them 1/2 Sonic and 1/2 Electric (applying only BoTT), or make them 1/4 Sonic, 1/4 Electric, 1/2 Force (applying BoTT first, then applying Force-Charged).  If he applies Force-Charged first, then it effectively becomes over-written by BoTT and deals 1/2 Sonic, 1/2 Electric, and 0 force, according to the RAW of that feat.

Note that splitting up the energy damage into resistable types isn't optimal, since both Sonic and Electric resistance would apply (albeit in smaller quantities), so if he just wants BoTT for the split damage types, definitely suggest he doesn't take that feat.