Alright, here's the deal. I'm in Castle Palamecia, and I open a monster in a box. Out comes a queen snake lady and five purple lions. (can't remember the names) They kill Maria, then Firion had 2000HP and one of them attacks him and it does 40 damage but he just dies. The same thing happened to Ricard and Guy! What the hell happened? I was quite annoyed and didn't try again!

If you are in Castle Palimecia and you die to Lamia Queens, thats a major sign that you need to train more.

The purple items were probably either Devil wolves or Chimera Spynxs, niether which you should have trouble with.

I think some enemies have a chance to do a One Hit KO every time they attack, regardless of their damage. I've run into this problem before as well.

you need to train more and i believe those monsters have one-hit KO attacks(does not work 100% of time)

i think the lions were couerls they get annoying and i think their attacks cast death so that explains ur immediate death
try get ur magic defense up
i think its magic defense
i just keep training and after a long time i become almost immune to special attacks lol