Its the most usefull item in ur build because u will need it in the end game for tanks or to kill high health champs like sion,trynda or jax. With this item u will do 1000er crits.

u can buy in place of the second Bloodthirster a Stark's Fervor, but only when u are the first who jump in a teamfight. It is better because for a moment u can tank a bit till ur team comes in. Approximately u need only 3 hits to full life.