“The Black Shard is a weapon that can be obtained by "defeating" the Knight in Chapter 3. It can be equipped by Kris (and Noelle by modifying the game). It deals significant damage against Dark-Type Enemies, such as Titans and Titan Spawn. It has no armor counterpart, as opposed to the first two weapons from bonus bosses”
“... how is this a weapon? [When attempting to equip it to Susie]”
“I... shouldn't use it [When attempting to equip it to Ralsei]”
ok ok so, again entirely non-player perspective here, but the weapon you specifically obtain by ‘defeating’ the knight can only be used by the two people connected to the knight in some way. kris is a mole who helped orchestrate the very defeat that earns you the shard, and noelle is both the daughter of the one truly in charge of the knight’s operation, as well as the only other lightner besides carol to be aware of YOU (following the weird routes), as well as her family being all of the most viable knight identity candidates.
the only two people you can’t equip it with are susie: who is currently unaware of literally everything and only responds to the shard by asking how it could be used as a weapon, which i interpret as either a further highlight of her unawareness (ie, genuinely considering it to be unassuming and useless) or even possibly relating to her arc with becoming a healer and relying less on violence and anger as a defensive front and ralsei: who is both infinitely aware of everything and constantly lying by omission about it, and very vaguely responds to the shard by saying he shouldn’t use it.
i first interpreted it as something like “he’d be more than capable of using the shard or even possibly corrupted by due to his mysterious nature,” but now that i also know it can significantly damage darkners, titans and titan spawn (which ralsei can potentially be either one of) i think there’s a secondary interpretation where he shouldn’t use the shard because it would severely hurt him, like the full sword did to tenna. but then that begs the questions:
• how can ralsei even be severely injured when, unlike tenna, he just vanishes after the knight hits him? • if he’s incorporeal, and tenna + other darkners clearly are not, why is he incorporeal in a way they are not? • can petrified darkners truly die if left in the wrong dark world, or only if noelle uses snowgrave on them?
to me, the current best working theory is that he’s pure darkness like his dark world (guess what else is pure darkness in deltarune) (it rhymes it tighten), and if you squint enough it could also imply that Ralsei is either (1) concerned with his health as it pertains to being useful and needed by the fun gang, ie “I shouldn’t use this or I won’t be able to help you anymore,” or (2) starting to consider his wellbeing and boundaries as a person, as in “I don’t want to use this, even if you want me to” / “I don’t think I should use this, even if you think I should.” and of course there’s always the third secret option where it’s both/neither, but in any case I think they’re both pretty viable interpretations, especially because ch4 centered on ralsei’s self perception a little bit more and gives him more moments of self expression than the last 3 chapters (thinking specifically of when he and susie both yell “WHO THE HECK ARE YOU” to tenna).
idk how relevant it’ll ever turn out to be, or even if I’ve covered all there is to cover about it (emphasizing again I am a non-player and I’ve only ever watched it being played), but considering the setup of asgore’s black shard and the next dark world most likely being created by him I feel like there’d have to be an answer soon. knocks on wood