Necromancy is targeting a Karmic Guide in my graveyard. When it comes into play it becomes an enchant creature, but it cannot be attached due to protection and will be put into graveyard as a state based action. Here is part of the oracle text of Necromancy:

When Necromancy enters the battlefield, if it's on the battlefield, it becomes an Aura with “enchant creature put onto the battlefield with Necromancy.” Put target creature card from a graveyard onto the battlefield under your control and attach Necromancy to it. When Necromancy leaves the battlefield, that creature's controller sacrifices it.



Is “that creature” still referring to Necromancy although it was never attached (as a creature) to that aura it becomes?

This is a recurring question; for the answer, we only need to look at Gatherer for existing rulings.

If the creature card put onto the battlefield has protection from black (or anything that prevents this from legally being attached), this won’t be able to attach to it. Then this will go to the graveyard as a state-based action, causing the creature to be sacrificed. (2008-04-01)

Let's remember that we have lots of great tools to help us with (some of) our questions - and many tools that show us the Gatherer rulings (including web sites, phone apps).

d:^D