Deponents in the Past

Deponents (mediopassive-only verbs with active meaning) form their past exactly like other mediopassives - you just have to know the aorist because there is no active to fall back on. The contracted deponents take -ήθηκα: θυμάμαι → θυμήθηκα (“I remembered”), φοβάμαι → φοβήθηκα (“I got scared”), κοιμάμαι → κοιμήθηκα. φαίνομαι is irregular: φάνηκα (“it seemed / turned out”). And έρχομαι is the odd one out - its past is the ACTIVE-form suppletive ήρθα (“I came”), the one deponent whose aorist looks nothing like -θηκα, so you recognise it rather than derive it. The imperfect of every deponent is the ordinary -όμουν series (θυμόμουν, φοβόμουν, ερχόμουν).