It cant be targeted, damaged, destroyed, exiled, or otherwise interacted with in any way it essentially ceases to exist
To make things easier, I will underline cards that I think are particularly elite
Since he essentially gains +3/+3 each time he takes damage, and gives you three rad counters at the same time, any repeatable ping effect can grow Strong to obscene proportions and Mill your entire deck, opening the doors for a Thassas Oracle win the next turn
As a whole, it's hard to point to a stronger release in terms of artistic quality, and that's largely in part to these things I mentioned: a solid, fantasy-filled story, the right blend of old and new, and the leadership to encourage classic mark making with contemporary illustration, looking back with respect, but forward at the same time