ok so what lvl do you have to be to battle him?

actually there is no specific level (just be toxic. fly also helps) and have won all gym leaders.

Also the guy's mew's levels will all be 10x your highest pokemon level - You don't get any prizes or extra stuff for killing all mews so just restart battle after 1

Thank you for the info guys will give it a try when i get to the point of being able to buy toxic thanks again

No lv needed toxic + fly = dead mew thts it tho I suggest using a golurk for it or golett

The best way to beat the Mysterious trainer is to use a golurk with toxic, fly and megahorn. If you can't afford toxic then use sludge instead because it has a chance of poisen the pokemon. For fly you have to beat zapmolcuno or maybe someone will teach your pokemon fly if you pay for it or just ask for it.

Thank you people for the very useful information you have given to me i am sure i will get tot the point i can battle him

Just complete all the gym fights then save coins to buy toxic then beat zapmolcuno(at npc)to get fly move then go to battle the mysterious trainer just use toxic then use fly until the mew dies or faints

fly is the best move to use along with golurks. Also shadow ball works well