rakshasa is a pretty formidable spellcaster, the Nazathurne rakshasa is a whole different story. It has no spells of its own, but isn't completely devoid of magical ability. Instead, this rakshasa can meld with the shadows and travel through them. Its lack of arcane knowledge is replaced with physical knowledge, which it uses to inflict devastating damage.
D&D has a few different rakshasas. The standard ones are pretty cool and Anthony S. Water's illustration for the 3.5 rakshasa is probably my favourite illustration in the Monster Manual, if not all of D&D illustrations. Other books added further rakshasas with more specific themes. Instead of being a sorcerer like the standard, the nazathurne is a rogue/shadowdancer.
The rakshasas are a set of demons from Indian mythology. Actually, they're more the Indian equivalent to the Japanese oni than European demons. Since both Hindu and Buddhism believe in reincarnation, sometimes rakshasa are the transformed or reincarnated form of a wicked person. The whole tiger-headed thing, though present is South Asian art, is exaggerated a bit by D&D. In mythology, a rakshasa can have the head of different animals or deformed features. Especially strong ones have multiple heads and limbs.
Book suggestionn du jour is The Ultimate Ilustrated Guide to Knives, Swords, Daggers & Blades by Harvey JS Withers and Tobias Capwell. It's a two volume collection filled with images of edged weapons (some polearms, not that many) that's a good resource and fairly compact. It's pretty Euro-centric, but there's still a fairy decent amount of space dedicated to the swords and knives of Africa and Asia. The knife that the rakshasa is wielding in the image is an Indian pichangatti.