Chi Shield

"Chi Shield" is an ability some monsters (namely the Sea Squirt and the Sea Fiend ) have. By sacrificing Skill Points, they are able to block a part of the incoming damage- and if they have enough Skill Points, they can theoretically block all incoming damage.

The easiest way to overcome this is to attack unrelentingly, not giving the monster enough time to recover enough skill points to make the Chi Shield matter. Another, more theoretical, method involves blocking the monster's abilitiy to recover skill points (though this may not be possible without hacking the game.)