Legends of Runeterra has many card effects that are common enough that they get their own keyword - a word or two that immediately tells you how the card works. Let's take a look at the Obliterate keyword.
Completely removed from the game. Doesn't cause Last Breath and can't be revived.
Destroyed, with no evidence left behind. Completely erased from existence; that's what it's like to be hit with Obliterate.
Obliterate removes a unit from the game, bypassing Last Breath. As it was not killed, it cannot be revived either. Rude.
Keywords that Work Great with Obliterate
Recall allows you to pull an ally who has an Obliterate effect back into your hand, so it can be played again. Destroy the world all over again!
Playing Against Obliterate in Legends of Runeterra
At present there is not much that can be done about Obliterate, as the keyword is relegated to a single card and it is not a spell that can be interrupted or hit with Deny. Keep the game from going to 10 Mana if you want to avoid seeing She Who Wanders.
Example Legends of Runeterra Obliterate Cards
She Who Wanders is the most notable example of Obliterate in the game, erasing from the game all units with 4 or less Power from the table and from each players' hands. That's most of the units in the game! She used to be the only card in the game with the ability until Rising Tides was released.
Devourer of the Depths utilizes the ability to a much smaller scale, only destroying a single unit as opposed to a bunch of them at once, but it can still be powerful.