Whenever a Swamp you control enters, choose one — • You draw a card and you lose 1 life. • Dread Presence deals 2 damage to any target and you gain 2 life.
2019-07-12
A Swamp is a land with the subtype Swamp, not any land with a mana ability that produces black mana.
2019-07-12
If you choose the second mode and the chosen target is an illegal target by the time Dread Presence's triggered ability tries to resolve, the ability doesn't resolve. You won't gain 2 life, and the ability won't change to the first mode.