This is an irregular verb. It follows the conjugation pattern of the verb odiar.
Present:
A Laura medeia conflitos no trabalho.
Laura mediates conflicts at work.
Imperfect:
O Miguel mediava aquelas reuniões.
O Miguel mediava essas reuniões.
Miguel used to mediate those meetings.
Future:
A Ana mediará a discussão amanhã.
Ana will mediate the discussion tomorrow.