Adding a new key to a full account

So I have all the campaigns atm and I know someone who's quiting GW and only has the prophesies campaign.
If I add his key to my account what will happen?
Do I get more char slots (what i pressume)? If it is so how many slots do I get more?
TX in advance

Any already existing account can't be merged with other already existing accounts.

So....basically nothing will happen when you try to add your friends key to your account, other than a message stating the key was already used.

Exactly. What you will have is 2 accounts.

closed