Samegaki

+1 Suggestions above are considerable good but the ones that stood up the most are 10% EXP gain and 10% Hidden Ability. For shiny encounter since it's 1/8192 (0.012%), I would love to see a happy hour with 1/6826 (0.0146%) instead.

Story service Kanto 5th badge to Sinnoh E4 with Subway and Teleport Payment sent to Servicer Manav861

Misdreavus can be found in Mt. Silver

Taking it down is quite difficult if you're under-leveled but there is a way. You can use/lend any Electric type mons to paralyze his Mewtwo and use any mons with Dark & Ghost attack moves.