the petrified - a mob that protects hostile mobs

so we have zombies that primarily do melee attacks (with the exception of the frostbite), and skeletons that primarily do ranged attacks (with the exception of the wither skeleton), what if there was another undead that primarily blocks the player's attacks?

i propose, the petrified. this mob would spawn in the overworld (and have variants similarly to the zombie and skeleton, but i won't get into them rn) and would get in front of a horde of mobs to block the player's attacks, but it'd be slower. it won't attack the player, but it's invincible. critical hits would have a chance to negate its invincibility temproarily, allowing for it to be killed.

these mobs would drop ossified plates, which i'll cover in another post.