Learn Portuguese (Portugal): Alguém veio ver a coleção de antiguidades. - Someone came to see the antique collection.

No, alguém (someone/anybody) is an invariable pronoun, meaning it never changes form. Even though it represents an unknown person who could be male or female, it is always treated grammatically as a third-person singular subject. That is why we use the singular verb veio here.

Which verb is veio?

Veio is the past tense (Pretérito Perfeito) of the verb vir (to come) for the third-person singular. Because alguém acts as a singular subject, we use this form. Vir is highly irregular, so its past tense forms just need to be memorized!

Why isn't there a word for "to" between veio and ver?

In English we say "came to see", but in Portuguese, verbs of motion like vir (to come) and ir (to go) can be followed directly by an action verb in its infinitive form (like ver) to express purpose. No extra preposition is needed.

Why say coleção de antiguidades instead of using a single adjective for "antique"?

While English often places nouns right next to each other so one acts as an adjective (like "antique collection" or "water bottle"), Portuguese usually links the two nouns with the preposition de (of). It literally translates to "collection of antiques".