-en verbs drop the -e in their past tense form. Otherwise, their conjugation pattern is fully regular. 
We'll use the verbs ta hapen (to happen), ta ɯiqen (to weaken), and ta sharpen (to sharpen), as examples.

3rd Person Singular Present Tense: hapens, ɯiqens, sharpens
Past Tense: hapend, ɯiqend, sharpend
Progressive Tense: hapeniŋ, ɯiqeniŋ, sharpeniŋ

Past tense forms can be used as adjectives
Examples: Ћe ɯiqend fyhteur. Ћe sharpend nîf.