Today I haven't my Battle Tower, but I've read on this forum you need your "Trainer" for this "skill-thing"
I hope I'm not wrong? But for sure, I know, other people can help you!
On 7th of february 2015 : I start a new adventure in the Divinity world of Original Sin, it's a Fantastic Freaking Fabulous Funny ... it's my All Time Favorite One !