Learn Spanish (Latin America): Tú actúas como si ese duende te hechizara.

The phrase como si (as if) always requires the imperfect (past) subjunctive to describe a hypothetical situation happening right now. Even though the acting is in the present (actúas), the goblin isn't actually bewitching you. The imperfect subjunctive (hechizara) signals that this is an imaginary or contrary-to-fact comparison.

Could I say como si ese duende te hechizase instead?

Yes, grammatically you can use the -se ending of the imperfect subjunctive (hechizase), and it means the exact same thing. However, in Latin America, the -ra ending (hechizara) is used almost exclusively in spoken Spanish, so it sounds much more natural here.

Why does actúas have an accent mark on the 'u'?

The accent mark breaks the diphthong (the natural blending of the 'u' and 'a' vowels). Without it, the word would be pronounced as two syllables with the stress on the 'a' (ac-TUAS). The accent forces the vowels into separate syllables (ac-tú-as) and places the spoken stress on the 'u'.

Is te a direct or indirect object pronoun in this sentence?