Lazav, the Multifarious

When Lazav, the Multifarious enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
{X}: Lazav, the Multifarious becomes a copy of target creature card in your graveyard with mana value X, except its name is Lazav, the Multifarious, it's legendary in addition to its other types, and it has this ability.

Murders at Karlov Manor Commander

When Lazav, the Multifarious enters the battlefield, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
{X}: Lazav, the Multifarious becomes a copy of target creature card in your graveyard with mana value X, except its name is Lazav, the Multifarious, it's legendary in addition to its other types, and it has this ability.

Ravnica Remastered

When Lazav, the Multifarious enters the battlefield, surveil 1.
{X}: Lazav, the Multifarious becomes a copy of target creature card in your graveyard with mana value X, except its name is Lazav, the Multifarious, it's legendary in addition to its other types, and it has this ability.

The List

You perform the actions stated on a card in sequence. For some spells and abilities, you'll surveil last. For others, you'll surveil and then perform other actions.

Any effects that applied to Lazav before it becomes a copy of another card will continue to apply once it's become a copy. The same is true of any counters that are on Lazav.

Because Lazav isn't entering the battlefield when it becomes a copy of a card, any "When this enters the battlefield" or "This enters the battlefield with" abilities of the copied card won't apply.

If a card in your graveyard has {X} in its mana cost, X is considered to be 0.

If the copied card has an ability that can be activated only once each turn, copying that card a second time will allow you to activate the new instance of that ability.

Lazav copies exactly what was printed on the original card and nothing else, except the characteristics it specifically modifies. It doesn't copy any information about the object the card was before it was put into your graveyard.