So far, I've found Bottled Blackhole [2] and Broken Lantern [3]. Are the ones in Chapters 1 and 4 obtainable yet?
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Well, if you mean the one in Chapter 4, that's what I'm trying to find out (I assume probably from some magnet-related contraption, but nothing currently fits the bill).
You get Bottled Blackhole by using an evocation on the Black Hole Bomb in Chapter 2, and the Broken Lantern by using an evocation on the Gravity Pad in Chapter 3.
For Chapter 1, I couldn't find a hint at all, unlike in the other three chapters.
Chapter 1 and 4 secret artifacts will be available in chapter 8 and 11, respectively. Anyway, join the official MVZ2 Discord for updates, sneak peaks and spoilers of upcoming chapters (which was the information i just gave came from). You should also ask questions on the MVZ2 Discord to have more chances of getting an answer since there're more active people there.