Rubean

Rubean turns zombie that eats him into crystal, which doesn't do anything but shields zombies until it's destroyed.

Strategies
Use him against Bucket heads, Knight Zombies and Amber heads. Their hp are very high and they can be instakilled very easily.

Crystalized zombies work as graves - they shield zombies, so good strategy is to use catapults or strikethrough plants. They can be destroyed by shooting at it, using explosive plants against it or simply using

Plant Food Ability
Plant Food: It turns 5 random zombies on lawn into crystals.

Trivia

 * It's twenty ninth plant by WaterBlazek.
 * The name is pun on words Ruby and Bean
 * It's name sounds more like Polish word for Ruby; Rubin.