I know how to give the sword:

Absorb 20 health per hit

Absorb 20 stamina per hit

However, while I know how to put soul trap on it - it means having soul gems. Is it possible to somehow place Soul Siphon (as the perk) on the blade?

Other thoughts? I want to play Elric of Melnibone and conceptualize him as: High Elf with all level points put into magicka so that he is dependent on his sword for health and stamina.....

You can put only 2 enchantments on any item. I made Stormbringer out of a daedric sword with soul trap & health drain, Mornblade is a daedric sword with soul trap & stama drain. Soul Siphon is a perk you need to pick and keep. You really need to have enchanting at 100 and take every perk if you want to roleplay Elric.

Well, I have already played so many hours I was going to make the sword in the CK: giving it 3 powers (absorb health and stamina: 20 each) and soul trap - but was hoping I could put a 25% soul siphon instead - b/c that would fit the sword better so it didn't need soul gems but also didn't have infinite charges (in the books the sword can stop feeding Elric when sated).... I was going to give the sword to my character at the very beginning (level 1) but never give him stamina or health as he levels up so he is dependent on the sword and fragile.