Well, mostly because I shouldn't have trusted my memory I thought it gained +X/+0 whenever it blocked, instead of whenever it became blocked. So I figured it could block and kill all my smaller creatures. No change needed. About Brunting Wurm: At 4/4 he's a beast! Four damage seems too much to take each turn. The fact that there aren't a lot of creatures with casting cost 4 points lower than their power means he isn't going to killed by blockers, and four tougness puts him out of range of most removal. I was going to suggest making him 3/3. He needs 3 power to remain a threat. He doesn't get a name like Brunting Wurm if all he dies is slither by. But I think three toughness is still pretty good for a creature who won't die in combat. Also thinking of the possible abuse if one was to combine him with some kind of Lure effect, I propose 3/2.