Ludevic, Necrogenius // Olag, Ludevic's Hubris — ruling 1

You choose which exiled creature card Olag is copying as it transforms. It doesn't transform and then become a copy.

Ludevic, Necrogenius // Olag, Ludevic's Hubris — ruling 2

Olag remains a copy of the creature card you choose even if that card later leaves exile.

Ludevic, Necrogenius // Olag, Ludevic's Hubris — ruling 3

It's possible for Olag to become a copy of a card with the daybound keyword ability as it transforms. If this happens, it doesn't transform as it becomes night.

Ludevic, Necrogenius // Olag, Ludevic's Hubris — ruling 4

If there are no creature cards exiled with Ludevic as it transforms, perhaps because those cards were removed from exile in response to its activated ability or it transformed another way, Olag won't be a copy of anything. Olag will simply be its 4/4 self with no +1/+1 counters.

Ludevic, Necrogenius // Olag, Ludevic's Hubris — ruling 5

If Olag becomes a copy of another transforming double-faced card that doesn't have nightbound, such as Delver of Secrets, abilities of it gains or other effects may cause it to transform. If it transforms this way, it does not become Ludevic again. The copy effect continues to apply and its characteristics don't change. If the creature it is a copy of has a triggered ability that occurs when it transforms, that ability will trigger.

Ludevic, Necrogenius // Olag, Ludevic's Hubris : règles, fonctionnement et interactions (MTG)

Ludevic, Necrogenius // Olag, Ludevic's Hubris is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Whenever Ludevic enters or attacks, mill a card. , Exile X creature cards from your graveyard: Transform Ludevic. X can't be 0. Activate only as a sorcery. As this creature transforms into Olag, Ludevic's Hubris, it becomes a copy of a creature card exiled with it, except its name is Olag, Ludevic's Hubris, it's 4/4, and it's a legendary blue and black Zombie in addition to its other colors and types. Put a number of +1/+1 counters on Olag equal to the number of creature cards exiled with it.

How it works : Ludevic, Necrogenius // Olag, Ludevic's Hubris

Original English text — Wizards of the Coast / Scryfall

#1September 24, 2021· Wizards of the Coast
You choose which exiled creature card Olag is copying as it transforms. It doesn't transform and then become a copy.
No other card is named in this ruling.
#2September 24, 2021· Wizards of the Coast
Olag remains a copy of the creature card you choose even if that card later leaves exile.
No other card is named in this ruling.
#3September 24, 2021· Wizards of the Coast
It's possible for Olag to become a copy of a card with the daybound keyword ability as it transforms. If this happens, it doesn't transform as it becomes night.
No other card is named in this ruling.
#4September 24, 2021· Wizards of the Coast
If there are no creature cards exiled with Ludevic as it transforms, perhaps because those cards were removed from exile in response to its activated ability or it transformed another way, Olag won't be a copy of anything. Olag will simply be its 4/4 self with no +1/+1 counters.
No other card is named in this ruling.
#5September 24, 2021· Wizards of the Coast
If Olag becomes a copy of another transforming double-faced card that doesn't have nightbound, such as Delver of Secrets, abilities of it gains or other effects may cause it to transform. If it transforms this way, it does not become Ludevic again. The copy effect continues to apply and its characteristics don't change. If the creature it is a copy of has a triggered ability that occurs when it transforms, that ability will trigger.
No other card is named in this ruling.