Soo anyway just wanted to clear this all up for you boys.
First Head Butt's stun effect works like this;
Stun chance and duration seems to be related to INT difference between caster and target.
Next for the spells in question and what element are the effects based on it's this.
Magnetite Cloud (This is a Breath type spell)
Deals earth damage to enemies within a fan-shaped area originating from the caster.
Additional effect:
Weight is wind based, only the initial damage is earth based.
Mysterious Light (This spell is CHR mod not INT)
Deals wind damage to enemies within range. Additional effect: Weight.
Due to it being a CHR stat mod the damage, and additional effect is your CHR - opponent's CHR with a multiplyer of 1
For any spell in the game the chance of resist is
Quote:
Resists lower magic damage negatively. A spell can be resisted only in these increments:
1/1 (No resist) 1/2 1/4 1/8 1/16 (Full resist)
An exact formula for resistance is unknown, but for elemental resists there are tiers which affect how often one resists that element. For example 320 resist is the known cap. When fighting Tiamat, with 320 fire resist Tiamat's magic damage will be fully resisted ~95% of the time.
Magic ACC seems to lower chance of resist. As does BLU's 2hour, best example BLU G5 fight and using Frost Breath.
Both Burst Affinity and Convergence increases magic accuracy as well.
That being said, there is not a 100% way to increase the duration of an addition effect. There are too many outside factors that effect the duration that using one type of equipment over another will work everytime.
One final thought, When looking at the ammount of MP that each spell costs, keep in mind that Magnetite Cloud is a Breath type spell, like all breath spells they have different set of rules when it comes to how much damage they can do. The only stat mod is your HP, yes they cost a lot of MP but they can do massive amounts of damage when not resisted.