Its a very late game build the objective is to get to your 4th-5th item you should be hitting hard with abilities around 400-600 each and activating deathmetal to crit around 700 on tanks and 1400 on dps at full build. The key is to NOT die early!
IF they have an adc you cant get away from i recommend going deso spear instead of necro thats only if you cant keep the stacks.
If you dont think you can keep the stacks on necro.