Magic Reduction Aura

[Vinz]

In DotA, the Hero Rubick has a Magic Damage Reduction Aura.

a.) is there any built-in ability that I am missing?
b.) or is it coded, and, if it is, is Magic Damage Reduction from items instant when you add the ability?(*)

(*) There's some delay in damage/armor increasing abilities, so there might be as well.

 

[Malhorne]

Elune's grace can give you magic armor reduction
Just trigger a pick everyone.

 

[UndeadImmortal]

I'm sure they use either a custom damage system or trigger and pick every unit that has the aura buff. Elune's Grace stacks afaik compare to the Magic Damage Reduction item ability.

 

[Vinz]

Okay thanks.