>>534319835
only way to get mr xp
dont sell prime/special versions of stuff like wraith/prisma/dex
check the wiki for weapons used to make other weapons
each frame fed to the helminth gives mastery xp or it was each helminth level
railjack/duviri intrisics also give xp per level on them
most annoying thing you will find to get that last bits of mr is pets and k-drive boards,so i would start grinding ventkids standing every now and then to save yourself the trouble in the future