Without 1.21 features enabled, the bad omen effect does nothing when the player is near a village in the Nether. However, with 1.21 features enabled, it will convert into raid omen.

To reproduce:

1. Create a new world with 1.21 features enabled.
2. Spawn a villager and place a bed in the Nether to create a village.
3. Drink an ominous bottle near the village, noticing that the bad omen will convert into a raid omen despite raids not being possible in the Nether.