is ok but if u arent rushing it or getting it 2nd it takes to long to stack to really be meaningful for him.
on the mostly ap build you have ROA and MASK which both share the
build path and passive which is a waste of stats /gold
personally i build him
as my core items. then everything from there is situational depending vs ap or ad.
but then again i build maokai pretty much the same way with the same core items.
you dont need rylais for a slow cuz your Q already slows. you arent really going to proc the slow passive with any other ability to make it efficient to dump into.
if you wanna be ad malphite you can go
into tank.