I just wanna ask if how could I obtain some Ethernal Items?
Eternal Item drop is random, eventually you will get the drop, the drop rate is low, just keep farming.
high Luck improves your chances of getting an Eternal Item to drop. Eternalized Set also improves your chances. Treasured Perk improves your chances even more. if you look in Codex > Feats >, there is a Feat where if you defeat a Mythic Monster, your reward is an Eternal Item. if you are in a real hurry to get Eternal Items, Salvage Legend items for Dust and then use the Dust to unlock Eternal Items in the Codex and then you can use Dust to buy Eternal Items from the Codex.