I've Achieved Immortality, So What's Wrong with Playing a Sacrifice Build?

[Fantasy + invincible + scheming + play the pig to eat the tiger] Overworked office drone Lu Xuan is sent to a fantasy world by a heaven-chosen truck. After burying his cheap dad, he gets kidnapped. While unconscious, he awakens an absurdly powerful talent! [Immortality!] [Maxed-out comprehension!] After an accident, Lu Xuan discovers that practicing forbidden arts seems to be a faster way to grow stronger, so he takes a very different path. Forbidden Art! Bloodmark Sacrifice: Mark an enemy! For every year of his own lifespan he sacrifices, the enemy loses the same number of years! Forbidden Art! Dark Vortex: At the cost of letting darkness grow in his heart, create a vortex in the ground that devours all enemies within its range, then wraps them in a black sphere and annihilates them. Peerless Murderous Weapon! Longnight Godslayer Bow: Powered by lifespan, the more years sacrificed, the greater its power. A million years of lifespan is enough to slay an Immortal Emperor! Even with so many forbidden arts and vicious weapons at his disposal, Lu Xuan remains cool as a cucumber and loves playing the hidden trump card! Hundreds and thousands of years later, Lu Xuan becomes a fiend whose name strikes terror into all who hear it! Immortal Emperor: Please, somebody stop him! He’s nearly emptied my Immortal Emperor Palace! Primordial Clan King: Why the hell won’t this bastard stay dead, no matter how many times we kill him?! Human Emperor: As long as Lu Xuan is here, humanity stands! Lu Xuan pulls the spear from his chest and scoffs. “A mere mortal wound! What’s there to fuss about?” The Myriad Worlds are losing their minds. Good grief! That bastard really is impossible to kill!