If the recently spoiled Arixmethes, Slumbering Isle were to enter the battlefield while there's a blood moon out, does he enters tapped, untapped, or does his controller decide?
I personally think he would enter tapped as he would exist as a non-land creature (with all his abilities) on the battlefield unless the (single) replacement effect stating he enters tapped and with the slumber counters has already been applied to him entering the battlefield. Basically, we'd need to apply it for blood moon to realize our living island actually is a mountain. But I'm not sure... is that reasoning correct?
Thanks in advance!
You are correct, there is a dependency between Arixmethes' ability and Blood Moon. Blood Moon can't apply until after Arixmethes' ability applies, which cannot happen until after it has slumber counters placed on it. So it will enter the battlefield tapped with 5 slumber counters on it as a Mountain.