There's something key to note for both Agnes and Ezzie and I love that I get to use them for comparisons because it's a great way to expand my lore for people when the times come. It's early in Agnes's story so I don't want to give anything away too much, but the KEY difference to note between Ezzie and Agnes is that Agnes is having a WILLING merging with an artifact, while Ezzie did NOT.
When an artifact selects its host, it wants the agreement OF the host to make a full merging. Agnes is in the process of doing that currently with hers. It's a very slow process that involves a lot of interaction for the artifact to slowly become one with Agnes and aid her as it sees fit.
Ezzie was NOT given this time, she was pulled out of her mother's womb and forced into a merging, which is why the artifact killed so many prior to her. Ezzie had a possible connection, which prevented her death, but now the artifact is in this forced-merge.
So what it'll look like is this:
Agnes's artifact is getting to know her as it merges, it knows where it is within her, how to react and move to her. It's basically like as it merges it's being dropped into the middle of a well-populated area with streets and a map. It knows where it's going, it knows how to get there. Because of this, Agnes can have great communication with the artifact and can call on it whenever she wants, because it hears her, it knows where to find her and where to find whatever it is she wants.
Ezzie's artifact was thrown into a cornfield, by comparison. It cannot see where it is. It cannot know who it's in. Sometimes - when situations get DIRE - it can see enough to react and help, but otherwise it's like it's not even there, because it has no idea who or where or what is even going on. If Ezzie wants to call on it to help her... sometimes it hears her and tries to respond... sometimes it hears her and can't respond... and sometimes it doesn't hear her at all.
Also important to note - every artifact has different things it does. Ezzie's won't get known very much because Ezzie has never been able to "sync up" with it like Agnes is. So I can tell you that if Ezzie COULD'VE "synced up" with her artifact, she would've been granted healing, shields, flight (by turning into a bird at will), and she can defend herself with a "magical" burst of lightning. This is hopefully a little familiar to you, as Adam ironically spoke about Adriel creating "artifacts" before, but joking that humans would likely never run into them, well... Ezzie's is one of hers, which is why the abilities are very similar to Adriel's natural abilities. Not all artifacts are made by her though, it was more just a nice coincidence.
Now Ezzie has her set of things she can "do" with her artifact (or could, had she merged properly with it), and Agnes has a completely different set. Each artifact has a strengths and weaknesses. Ezzie's was revealed to be cold, as it's too slow and not "dire" enough for the artifact to react in time to save her.
Agnes's... she's got some super fun abilities I'm going to have a shit-ton of fun playing with! I'll just say that and drop in
pictures of what a fully merged artifact might look like...