What does "Tough" do?

[caract]

Hello. I recently got Von Drakk Manor and noticed that Von Wilder is "Tough" and Vulnerable: magic. Now I know what vulnerable magic is but I can't find a description for Tough and the back of the card only explains the rules for Lycanthropy. I am guessing this was something included in the caverns of Roxor, which I don't have.

 

[caract]

I found out! It was on the Claw Tribe Barbarian card (knew I'd seen it somewhere)

For anyone wondering, it lets you remove a heart counter at the start of each activation.