Forum:Blood Mefist's effect

I'm curious to know, but lets say the effect of Blood Mefist's 1st is activated on my opponents Standby Phase while my opponent only has an Xyz Monster with 2 Xyz Materials on his/her field. Would my opponents take 300 or 1500? 108.13.254.251 (talk) 05:52, June 23, 2012 (UTC)