Sithras are elemental one-handed weapons.There are 7 Sithras,Fire,Cold,Lightning,Acid,Unholy,Holy and Poison.
Sithras require:Alchemy 100, Jewelsmithing 100, Weapon Smithing Mastery 100.
Alchemy makes the elemental blade. Each elemental blade requires, 2 of a specific Quality 5 Enchanting Mat, 1 Rare Ingot and 1000g.
JewelSmithing makes the Fibula(hilt). Each Fibula requires 7 jewels (specific too each element, same as Q5 Enchant Mat above.) and 1000 gold.
Weapon Smithing Mastery 100 puts the two parts together. This requires 5000g and in most cases 5 rare ingots. You can find the specifics on spreadsheets all around the internet.
Sithras aren't as viable as high quality transmuted weapons as far as a bang for the buck ratio. However, if you have the spare resources they are epic, and do tons of damage, especially if your mounted.