In pursuit of ultimate power, he would burn his world to the ground.

Memnarch

{1}{U}{U}: Target permanent becomes an artifact in addition to its other types. (This effect lasts indefinitely.)
{3}{U}: Gain control of target artifact. (This effect lasts indefinitely.)

Secret Lair Drop

"An imperfection in the perfect world? We can't allow that."

From the Vault: Lore

{1}{U}{U}: Target permanent becomes an artifact in addition to its other types.
{3}{U}: Gain control of target artifact.

In the blur between metal and flesh, Memnarch found madness.

Archenemy

Darksteel

{1}{U}{U}: Target permanent becomes an artifact in addition to its other types. (This effect doesn't end at end of turn.)
{3}{U}: Gain control of target artifact. (This effect doesn't end at end of turn.)

The effects of Memnarch’s abilities don’t end at end of turn, and they don’t end when Memnarch leaves the battlefield. Both effects last until the affected permanent leaves the battlefield.

You can use the first ability on a nonartifact permanent, wait for the ability to resolve, and then use the second ability on that permanent.