Is the damage of "mana burn" always the same or depends of jewels
with a full S+4 jewels hierophants burns my MP by 150 and 200 some times

hmm is hard to give a answer ...depends on the server

whats important, is the power of skill imo ... e.g. MB lvl 10 has 162 power which means ~162 MP or am i wrong?

Would it not also depend on Mdef of target and Matk of caster?
Specially since he says it differs already, i would guess that its affected by Matk also.
U could also ask him to do it some times and try to see the difference with jewels equiped/unequiped.

caster's m att + skill power vs target's m def

And btw, Mana burn can mc, that's when you're screwed d:

Someone told me that mana burn decrease a certain% of mp, but didn't test it so it is surely false.

ive never heard about that, but its still possible ...

No, look at the skill, it has x power, it is like a nuke, but it damages MP,not hp/cp.

i think dmg depend on the enemy's MEN

Mana burn is like normal nuke but it's calculated a bit diffrent ( lower * at damage and higher * on m def ) so with power 163 u will have a power like nuke with power ~80

men=mdef
mdef=magical skills resistance
any type of magical skills
curses,nukes(damaging type skills),mana burns and etc