Got this idea, hopefully it works and isn't to overpowered....
Addiction
6/6 Orange Evil Character
May band to a human evil character. OR if Addiction defeats a human hero in battle, take that hero prisoner. Cannot be prevented. If opponent plays a healing card, discard Addiction.
Wanted to capture the...well, addicting nature of being addicted to anything. I feel that the ability does that well. I like both the abilities and feel the "OR" balances it some. The banding to an evil character is nice, and the second part of the ability gives your opponent the chance to "fight" Addiction and win. I wonder if the "OR" is really nessacary, if the card would be to overpowered without it.