MEGA GENGAR IN MASTER LEAGUE! Pokémon GO Battle League

Mega Gengar Pokemon GO Wiki - GamePress

Mega Gengar Raid Guide For Pokemon Go

A Pokémon GO World Championships Celebration: A Basic Guide to Pokémon GO Battles

Master League Battle Team Rankings - Pokémon GO PvP

Best Mega Evolutions for the Pokemon Go Master League - Dexerto

Pokémon Go Master League Mega Edition: Best Pokémon - Video Games on Sports Illustrated

Pokémon Go Master League Mega Edition: Best Pokémon - Video Games on Sports Illustrated

Master League Infographic, Season 2 (article link in comments)

Best Mega Evolutions for the Pokemon Go Master League - Dexerto

Pokémon GO - To celebrate the recent update to Mega Evolution in Pokémon GO, for one day only, Trainers will be able to use Mega-Evolved Pokémon in the GO Battle League's Master

Pokémon Go' Mega Evolution Event 3: Start Time, Mega Gengar, Research Tasks & More