There are no Generation 2 Legendary Pokemon that can Mega Evolved so I'm making Lugia my pick as my last Generation 2 Pokemon that's getting a Mega Evolution. In Pokemon lore, Lugia is known be the "Guardian of the Sea" as explained in its Pokedex entries in games that feature Lugia. Lugia is also the leader of Articuno, Zapdos and Moltress as it's able to end the conflict between the three birds.
Pokedex Entry:
"True to its title as Guardian of the Sea, it's been said that Lugia can manipulate the water as if it's a weather conductor".
Ability: Guardian of the Sea
A custom Pokemon ability I've made up using Mega Meganium's Mega Sol ability as the basis idea. It means if the weather isn't currently raining, Mega Lugia's moves will be treated as if rain was active, which means Water types move deal 50% more damage, Fire type moves deal 50% less damage, Solar Beam and Solar Blade have power cut in half, Weather Ball becomes a Water-type move and power's doubled, Hurricane and Thunder get 100% accuracy, Recovery moves like Morning Sun; Moonlight and Synthesis heal 1/4 of user's HP. The reduction in the accuracy of the user's movements caused by the Abilities Sand Veil) and Snow Cloak) is ignored. Because Guardian of the Sea does not alter the weather itself, it is unaffected by the weather-negating effect of Cloud Nine). It also bypasses the Special Defense boost granted to Rock-type) Pokémon during sandstorm) and the Defense boost granted to Ice-type) Pokémon during snow. However the consequences will be Electric and Rock type moves are guaranteed to hit Mega Lugia with 50% more damage.
Base Stat and Total:
HP: 106
Attack: 130
Defense: 60
Special Attack: 130
Special Defense: 224
Speed: 130
Total: 780
Type: Water/Flying
Pokemon is owned by Nintendo, fanart is done by me.
by LightInteractives