: They are completely different in every way. Myrms have
: two blades of scythe attached to a femur bone. Ravanna
: has some bone-looking things that are much smaller
: than the classic Gridaksmas, and also have handguards.
There are a number of reasons why the Gridaksma Blades of the TFL Myrms are different than those employed by TWA Ravanna. Firstly, she is a hero, and heroes generally possess better quality armaments then others. Being the last Myrm and a friend of the Emperor would come with certain perks. Maybe a nicer set of blades is in order.
Or, weapons 'evolve' with time. A brief look at a sword from Dark Age England shows that it is vastly different in quality, style and material than those of Renaissance England. Availability of material, changing needs, or a sudden turn for the evil would all explain why the Myrmidons now use bone Gridaksma blades rather than the fancier metal ones. I can't imagine them mining for metals to make a blade, so bone (a commodity that soldiers have ready access to ) is a likely material.
Or Bungie could've given them bone weapon to show their evilness, and MJ didn't want Ravanna to appear evil.
LR