What happens to other land types (e.g. Legendary/Artifact) when some effects change the basic land types?
It might be a bit confusing, but 'legendary' and 'artifact' are not land subtypes, like Swamp and Mountain are. 'Legendary' is a supertype, and 'artifact' is a type.


  305.7. If an effect sets a land’s subtype to one or more of the basic land types, the land no longer has its old land type.


Evil Presence and Phantasmal Terrain do not remove 'legendary' and 'artifact', they influence the subtype. Hammerheim and Vault of Whispers don't have a subtype, but they will lose their abilities:


  The enchanted land loses its existing land types and any abilities printed on it. It now has the land type Swamp and has the ability “Tap: Add Black.” Evil Presence doesn’t change the enchanted land’s name or whether it’s legendary, basic, or snow.


(from the rulings below Evil Presence)

So a Hammerheim enchanted with an Evil Presence will still be legendary but only able to tap for black mana; a Vault of Whispers enchanted with Phantasmal Terrain set to 'Mountain' will still be an artifact land but only be able to tap for red mana.