Antlions

[Cat Grill Friend]

Why do you think that they are such seemingly important creatures? They help you storm Nova Prospekt, they're the first real threat you encounter after leaving the Citadel in Episode 1, semi-pivotal in Episode 2, and in HL: Alyx they're also the last new enemies you encounter I believe?

[Mλrtin2H]

The Antlions were domesticated by the Vortigaunts in Xen, that's why they know how to control them. They are an invasive species to they can probably be found allover earth. The reason you fight them in episode 1 in the city is because the citadel was keeping them out. After the citadel exploded, they entered the city.

[Ghidrah1]

For the juice/extract they provide the Vorts which they use for a number of things, food, happy hour, medicinal, increasing the energy output of a vort, etc.

[Portal90022]

Oh man

[Cat]

Their extract saved Alyx's life.