Urborg, Tomb of Yawgmoth

Each land is a Swamp in addition to its other land types.

Moira, Urborg Haunt

Menace
Whenever Moira deals combat damage to a player, return to the battlefield target creature card in your graveyard that was put there from the battlefield this turn.

Gix, Yawgmoth Praetor

Whenever a creature deals combat damage to one of your opponents, its controller may pay 1 life. If they do, they draw a card.
{4}{B}{B}{B}, Discard X cards: Exile the top X cards of target opponent's library. You may play lands and cast spells from among cards exiled this way without paying their mana costs.