Yes, you can still farm them after defeating Rykard.

can i still get this after killing rykard? like do the serpents still spawn

Sorry to all the others having trouble with farming this, I got ridiculously lucky and it dropped on the very first kill lmao. Never had this luck in my life, better do a lottery ticket today.
Silver scarab + silver tear mask, 198 discovery.

Took me about an hour at 274 discovery. It'll drop, and it's worth it.

For those who are getting lucky: yeah no sh1t probabilities are real and it's totally possible to get it quickly now move on let my unlucky a$$ grind

Got one after 25 runs! (50 Man-Serpent enemies killed).

Took me about 3 hours with 111 discovery to get two swords

i think im super lucky but i walked into elevator and in the room with all the dudes with poison on their heads, there was snake with the sword. i used weapon art and to my surprise i got it first try. i just stood there in shock cause i was just looking at the comments about drop rate before i went up there...but i want two cause i found out about this weapon in the middle of my faith-strength play through...this should be hell. good luck to you all. (also i clipped it because i felt lucky lol)

I managed to get a pair of these in one 3 hour session. Respected into a 60 arcane build , 230 discover. For those getting frustrated , keep at it , they will drop

Farmed this for several hours at 220 discovery and it yielded nothing but volcanic stones, but 270 discovery started giving me very reliable Man Serpent's Shield drops and I finally got two Magma Blades within the span of about 30 runs. So, for anyone else trying to farm this, I'd start at 270 and go from there