I can see if someone broke the rock it lived in. That would likely kill it. And I forgot Spiritomb is ghost and dark. And it would definately take some doing to beat it normally. If you are going to give him one, I would make it later, when our charcters are a lot stronger.
It's your call man. It'll be hard to beat unless you have a dark type. Ghosts are weak to dark types. Doesn't wonder guard not block stuff that has a type advantage? Because I remember roasting a lot of Shedinja with my Charizard in one game.
A wondertomb is a spiritomb with the ability wonderguard hacked into it, it makes since that the Human alliance would be experimenting and putting that ability into Spiritomb, and the Beggar is like a double agent for Team Plasma and the Human Alliance who has a much bigger goal in mind.