Trial Monolith can be summoned by crafting a spawn egg.
It has high health and performs long-range attacks that ignore armor, so obtain attack power and mobility before challenging it.
By defeating the Trial Monolith and using the Monolith Fragment it drops, you can craft weapons have the ability to use the boss's armor-piercing attacks.
Soul Damage
It means special damage that can ignore armor or invinciblity.
You can heal this damage by drinking a bottle of the soul.
Invader Monolith
Invader Monolith can be summoned by crafting a spawn egg which can be crafted by loots of the Trial Monolith.
It attacks all entities around itself.
It also deals you soul damage, but it disables your Soul Protection.
It is almost invincible, but drops enhancement items and one stack of Monolith Fragments.