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.