Deathrite Shaman

{T}: Exile target land card from a graveyard. Add one mana of any color.
{B}, {T}: Exile target instant or sorcery card from a graveyard. Each opponent loses 2 life.
{G}, {T}: Exile target creature card from a graveyard. You gain 2 life.

Mystery Booster 2

Ravnica Remastered

Explorer Anthology 3

Because the first ability requires a target, it is not a mana ability. It uses the stack and can be responded to.

If the target of any of Deathrite Shaman's three abilities is an illegal target when that ability tries to resolve, it won't resolve and none of its effects will happen. You won't add mana, no opponent will lose life, or you won't gain life, as appropriate.