It's a regular verb; just add -ed: "gathered"
Past is : Beat (itself) Past Particle : Beaten
"Gather" is a regular verb; therefore, its past participle is "gathered".
The simple past and past participle is had.
The past participle for shrink is shrunk.shrink / shrank / shrunk
"Encouraged" is the simple past and past participle of the verb "encourage".
The past participle of do is 'done'.
"gathered" is already in the past tense, the present tense of "gathered" is "gather"
The past participle is burst.
The past participle is drawn.
Been
The past participle (and simple past) is loved.
The past of the verb to gather is gathered.