Magic Resistance

Sorry for a bit of a lame question, but what exactly does magic resistance mean in BG? Does it cover just magic damage or all magic effects?
So, for example, if a creature has 50% magic resistance and you fire 4 magic missiles at it, does it mean there is 50% chance each of these missiles hitting the creature doing full damage, or does it mean each of the 4 missiles will hit it but do just half the damage? Or both of these? Also, does it impact every spell thrown at the creature (apart from those which bypass magic resistance), so e.g. throwing dire charm at it has 50% of being automatically blocked and in other 50% of occasions the saving throw is rolled?
Finally, is there a way to know from the fight log whether a creature has high (100% or more) magic resistance (so, spells like Lower Resistance would work to increase chances of some spells landing) or is completely immune to a spell (in which case there is no point in using Lower Resistance)? Or is the output the same in both cases, i.e. just 'Magic resistance'?
So, for example, if a creature has 50% magic resistance and you fire 4 magic missiles at it, does it mean there is 50% chance each of these missiles hitting the creature doing full damage, or does it mean each of the 4 missiles will hit it but do just half the damage? Or both of these? Also, does it impact every spell thrown at the creature (apart from those which bypass magic resistance), so e.g. throwing dire charm at it has 50% of being automatically blocked and in other 50% of occasions the saving throw is rolled?
Finally, is there a way to know from the fight log whether a creature has high (100% or more) magic resistance (so, spells like Lower Resistance would work to increase chances of some spells landing) or is completely immune to a spell (in which case there is no point in using Lower Resistance)? Or is the output the same in both cases, i.e. just 'Magic resistance'?
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Comments
Brief summary is that there are two kinds.
Magic Damage Resistance (like you get from the belt of inertial barrier) cuts down on the damage you take from spells that do “magic” damage. Magic missile and ADHW are examples of spells that do damage of the type “magic”
Magic Resistance (like you get from the holy avenger) reduces the chances that a spell will have its intended effect on you.
let's say that charname has 50% MR and 30% magic damage resistance and a magic missile or an other source of magic damage hit him.
he has a 50% chance to completely avoid the damage, the spell has not effect on him, but if he does not avoid the spell it any way does 30% less damage because of the magic damage resistance.
if a fireball hits him instead of a magic missile as the fireball does fire damage and not magic damage he has only 50% chance to completely avoid the spell, but if it does not happens he takes full damage as the magic damage resistance does not apply for fire damage, but only for the magic damage.
other sources of magic damage are the skull trap and holy smite, there possibly be more, and very few enemies are immune to them, while much more are somehow resistant to other damage sources like fire.
there is a lot to learn to play this game, it is not needed to be masters at it to beat it, but both the combat and magic systems are very complex compared to more modern RPGs.
Same concept?
The +1 physical damage from a +1 weapon is never blocked by Magic Resistance. However, some on-hit effects of magical weapons (like the +1d6 cold damage from Arrows of Ice) have a chance to be prevented by Magic Resistance, but not all of them do. It depends on the weapon.
magic resistance has a chance to completely block every not physical type damages, it is not always true as some of the damage sources ignores MR, there are some spells that ignore MR and it is often written in the spell description.
an example:
Implosion (Evocation)
This spell creates a rift in the earth beneath the target which implodes and closes in upon itself, crushing and burning the target and holding it for 1 round. The spell does 10d10 fire damage and 10d10 blunt damage. The victim can save vs. Spell for half. ”
All effects ignore Magic resistance.
https://baldursgate.fandom.com/wiki/Implosion
note that here the spell ignoring MR is not stated in the spell description, that is the part between the " ".
sadly not in the game, maybe something is in the game manuals, but usually you get this kind of information searching online, reading this forum or other dedicated sites or using a modding tool.
The original game was pretty inaccurate at this regard, not only some info is not available in the game, but some in game descriptions are also sometimes misleading when not wrong or can miss important things like in the example i gave for implosion.
and imo the EE did not much to solve this problem.
anyway i created this directory thread
https://forums.beamdog.com/discussion/75332/useful-knowledge-about-the-games-that-other-way-could-be-lost-please-help-by-reporting-links
that being a pined one is always on top of the section.
it contains links to all the relevant threads where detailed information on technical aspects of the game are discussed, that other way could be not easily available as buried under many new threads.
feel free to use it and to provide links to useful threads you find yourself, i will insert the link in the first posts for easy reference, as long as are not very old threads with obsolete and no more useful information due to changes of the game.