Assumptio won't halves the damages!

[Currently]

Where can I check it or edit the script?

[EvilPuncker]

are you using PRE-RE or RE?

[Mystery]

are you using PRE-RE or RE?

Where can I check it or edit the script?

According to what Evil has asked, Assumptio is very different in Pre-Renewal and in Renewal. Please take a look here for Pre-Renewal and Renewal differences.

Pre-Renewal:

Reduce damage taken from enemies by half for the spell's duration. Damage is only reduced to 2/3 of the original damage by this skill in PvP areas, including Battlegrounds and WoE areas. Cannot be cast inside a guild castle, but retains its effect after entering one. Assumptio and Kyrie Eleison cannot be used at the same time - they overwrite each other.

Renewal:

Double the target's DEF and MDEF.

Cannot be cast inside a guild castle, but retains its effect after entering one. Assumptio and Kyrie Eleisoncannot be used at the same time - they overwrite each other.

Take a look here as you can see where it's found:

//Finally damage reductions....
	// Assumptio doubles the def & mdef on RE mode, otherwise gives a reduction on the final damage. [igniz]
#ifndef RENEWAL
	if( sc->data[sC_ASSUMPTIO] ) {
		if( map_flag_vs(bl->m) )
			damage = (int64)damage*2/3; //Receive 66% damage
		else
			damage >>= 1; //Receive 50% damage
	}
#endif

[Currently]

Will it be at skill.c? or which source file?