Board Thread:Anything Goes/@comment-26503939-20160801132531/@comment-27517963-20160814231900

The observer is out for two reasons.

1. It doesn't have a face.

2. It was added in 0.15.0, while the others were added in 0.14.0.

Lily Pad, Tripwire Hook, Rotten Flesh

No hints as it would make this too obvious