Need important NPC build / items help

[KitsuneKid]

Ok, so I am running my first campaign. There is a character (the prince of the starting kingdom) who was framed for his sisters murder and forced to escape the kingdom. I am thinking ninja based because he is going to become a key ally to the PC's and he will be stealthy to spy, gather info, and elude capture through disguises.

His weapons will have the Merciful ability as he is a chaotic good character. That along with a ninja's vanishing trick/sneak attack would probably go along with his concept. Seeing as he is the prince of a kingdom though, he will have access to crazy magical items. What would you guys suggest as far as build and items?

[KitsuneKid]

Ok so the character will have a custom magical weapon. It's going to be a giant bastard sword (like cloud off of final fantasy 7) and it will have the merciful ability with an additional magical twist. I'm considering giving him cleave but his sword will go through people (without actually cutting them) and dealing non-lethal damage still rather than slashing through them.

[Morganstern]

My honest suggestion would be, don't. Just don't. A prince with access to magic items and resources befitting his station would vastly outshine most player characters of equal level.
It feels too much like a GMPC, and your players might not appreciate that.
I'd say if he's absolutely neccisary to the plot, keep him in the back; maybe he's not much of a warrior, but could instead sneak around enemies and scout, or try and feed the PCs vital information about the next area.

Though in all seriousness, I'd advise just not having him be in combat much if at all. :/

[KitsuneKid]

He will rarely appear in person. His function is mostly to feed the PC's information that he gains about the world/politics/discovery of evil plans etc.

He appears in the first session in which they fail to capture him but it introduces them to his character. Later on as they learn that he really isn't the villain he will end up contacting them and working with them from afar to overthrow the true villains.

If the NPC does appear, it'll be maybe a surprise appearance if I accidentally throw something too strong against them.