The off hand is only useful for cards - The damage add minimally/does not count hence you can use any lame dagger provided it has lots of slots. Thats why most people use
DDPT,DDSB,DDPB blades or MG in off hands. Blades do well for sins / Sinx but for a SN to access double attack - you should use a MG.
As for Ancient mummiers and Amon ra , I use a +7 Self Forged VVS Fire Damascus and it owns hard. I could do upto 6k with EDP on Amon ra with a +7 VVS Fire Dama and DDTP. No need to run sages as well. I suppose the OP has a top ranked Forger as his friend so getting Elemental daggers wont be a problem
