Does it stack? infact that question goes for all relics --- Currently Playing: Final Fantasy VI Advance, Chrono Trigger DS and Disgaea: Hour of Darkness Currently Awaiting: Nintendo 3DS, Golden Sun DS and Final Fantasy VI DS
They do not, nor do separate HP/MP Boosting effects stack. By which I mean a Muscle Belt (+50%) and Red Cap (+25%) do not yield + a 1.75 or 1.875 (depends how the game would calculate it!) boost, it just gives you Muscle Belt's effect cause that's the highest; apply exactly the same manner to MP.
And yeah, Earrings (and Magic effect of Hero Ring) is the only thing that stacks. I suppose if you want to be technical, Direct Stat Boosts stack, so 2 Thief Bracers with their +5 Speed do in fact give you +10 speed, but that goes without saying.
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