Actually we dont have Mythic Weapons.
I think Mythic Weapons Can be interisting and game changer.
I think we loot the 5 five lead in trial/Infinite Archive/Arena.
In Trial more difficult(Normal 5%/Vet 25%/Vet HM 40%) is the boss more chance you have to get the lead.
In Infinite Archive more arc you have finished and more you have chance to loot a lead.
The Weekly Infinite Archive Seller,sell 2 lead of Mythic Weapons.
PC EU PvE CP1800+(Play from Beta 12/02/2014) :
@MrCray78
Already finished all content in Infinite Archive 🥲