Shardmite

Behaviour and Tactics
It crawls up and down on vertical surfaces. Upon approaching it, it sprout long crystal spikes from its shell. While those spikes are extended, it is invulnerable. By attacking quickly, it can be taken off guard and killed before it sprouts its spikes.

It is also possible to bounce off its spikes by down-slashing. By repeatedly down-slashing, the Shardmite will retract its spikes briefly before sprouting them again, giving the player a chance to get in a hit between spikes while keeping distance.