How do you say magic and dark and evil in latin?

Answer 1

The answers suggesting "acerbus" or similar are incorrect. That word relates to meanings like "bitter".

If you are using the words as adjectives, the masculine forms are
magic = magicus
dark = obscurus
evil = malus

For nouns...
magica ars ~ the magic art
tenebrae ~ the dark, darkness
malum ~ the Evil

Answer 2

A lot will depend on the context, but one version of each is:

Magic = Veneficium
Dark = Acerbus
Evil = Malus

Edit:

As noted, much depends on context. Some comments on that:

I chose Veneficium for magic for its association with sorcery, potions, poisoning, etc. Magicus is a good general pupose word for magic, but since the request appeared to be toward the dark and evil side, Venficium seemed a better choice.

Acerbus does mean bitter (as do its English cognates), but it has other connotations also - painful, severe in reference to events; dark and gloomy, etc. Obscurus (and its cognates) definitely mean dark, but more in the senses of lack of light, vague, secretive. The term "dark magic" is used for that magic which kills, injures, or causes destruction. Acerbus seemed to fit better in that context.

At least we agreed on evil.

Answer 3

veneficus, a, um as adjectiv for (black)magic
magus,a, um for magic, magus=the mage

acer, acra, acrum is the adjectiv for dark, acerbitas, -atis,f =darkness

malus,a, um, with a short "a" is adjective for evil, the noun is malus, -i, m