Is Possessed Portal + Enduring Renewal a good combo (In that you can sacrifice creatures and get them back) or a GREAT combo (With the Enduring Renewal replacement effect letting you draw noncreatures through Portal)? I'm pretty sure it's only at the good combo level, and that since there is still a card draw event should ER hit a noncreature, Portal will replace it (though I suppose you could use this to mill creatures off the top until you hit a noncreature and get stuck), but I wanted to be sure it didn't manage to work the insanely good way.

There are two replacement effects trying to modify your card draws. Yo can choose to apply any one of them. After applying it, you check again for other replacement effects, and again until no new replacement effects want to apply to the modified event. Then the resulting event happens.

If you choose to apply Possessed Portal first, you skip the draw and that's all.

If you choose to apply Enduring Renewal first, you reveal the top card of your library. if it's a creature card, you put it into your graveyard. Otherwise, you again try to draw a card, but Possessed Portal's replacement effect still wants to apply, so you skip the draw. Not a GREAT combo.

Things like Abundance and Tomorrow, Azami's Familiar work well with Possessed Portal, because they replace a draw with a not-a-draw-but-still-an-extra-card-in-my-hand.