To me a breakable/fragile creature with 30HP makes no sense. Also this doesn't really fit in gravity as the combo is so obvious. However, I like the general/thematic idea of a breakable creature. Below are several ideas:
- make it have 1HP but be insensible to CC other than damage (poison, freeze, BB, etc...)
- make it a time creature which break when targeted by any CC but then turn it to an egg shell ( 0|X creature). Said eggshell can be rewound into the egg again.
- make it spawn a new creature (hidden inside) when broken
- other