Rudinn's body looks like a slug with diamond motifs on it. They have a single visible arm holding a diamond-shaped dagger and they wear a diamond-shaped hood on their head. Their eyes are also diamond-shaped. Rudinn's skin is white while the other colors of their design are various shades of greens.
Rudinn appears to care a lot about its wealth, constantly speaking about money and praising the person who paid them. They have even traded their beds for jewelry. They also don't seem to like their job very much, as they can be easily convinced to stop fighting, but their greed for jewels seems to be their priority.
Several Rudinns appear in Card Castle, including Susie's cell guard who she "invited" to the trash can, and two who sold their beds for "Normal everyday riches, acquired from a legitimate source."
If no enemy was defeated through combat, many Rudinns help to overthrow King at the end of his battle.
- Diamond Cutter: Diamonds spawning on the top of the Bullet Board and aiming somewhere in the fighting area
- Diamond Release: Diamonds spawning from below that move upwards, damaging on contact.
- Several conditions allow for Rudinn to be spared:
- Convincing Rudinn at least once
- Sparing 10 times
- Using X-Flatter or S-Flatter on Hathy while Rudinn is also present
- Using the Glowshard on Rudinn
- Lecturing makes all enemies tired, allowing Ralsei to Pacify them.
- Lecturing again tires Rudinn and allows it to be spared.
- Reading the manual also makes Rudinn tired.
- Long live the guy who pays us! [Neutral]
- I'm just a normal person... [Neutral]
- Face my Diamond Cutter! [Neutral]
- Yeah I guess that makes sense... [Convince]
- (Yawn)... What? OK... [Lecture]
- This ambivalent diamond isn't any girl's best friend. [Check]
- Rudinn drew near! [Encounter]
- A necklace of Rudinns blocks your path! [Encounter x2]
- Rudinn and Hathy blocked the way! [Encounter with Hathy]
- Various guys appeared! [Encounter with Hathy and other Rudinn]
- Smorgasboard. [Encounter with Hathy and Jigsawry]
- Smells like jewelry. [Neutral]
- Rudinn dislikes its boss, but doesn't care enough to quit. [Neutral]
- Rudinn is thinking about elaborate stones. [Neutral]
- Rudinn is glimmering plainly. [Neutral]
- Rudinn has no strong opinions one way or the other. [Neutral]
- You told Rudinn to quit fighting. It was utterly swayed. [Convince]
- Rudinn became enraptured! The GLOWSHARD disappeared! [Using Glowshard]
- Rudinn is starting to fall asleep. [Tired]
- Rudinn's luster begins to fade. [Low HP]
- Rudinn is alright with not fighting. [Spare conditions met]
- Rudinn's appearance and attacks are based on the diamond card suit.
- A group of Rudinns is called a "necklace" according to the battle entry text, "A necklace of Rudinns blocks your path!"
- This is presumably a reference to the fact that jewelry like necklaces can be made out of diamonds.
- Rudinn (along with Lancer, Hathy, Clover, King, Jevil and the uncredited King of Diamonds) were designed by kanotynes.
- With the exception of Jevil, all of kanotynes's characters were fully designed by March 2012 - 6 years prior to the release of Deltarune.