Nimble Obstructionist

Mana abilities can't be targeted. An activated mana ability is one that could add mana as it resolves, doesn't have a target, and isn't a loyalty ability. A triggered mana ability is one that could add mana as it resolves and triggers on an activated mana ability.

Triggered abilities use the word "when," "whenever," or "at." They're often written as "[Trigger condition], [effect]." Some keyword abilities, such as prowess and afflict, are triggered abilities and will have "when," "whenever," or "at" in their reminder text.

If you counter a delayed triggered ability that triggers at the beginning of the "next" occurrence of a specified step or phase, that ability won't trigger again the following time that phase or step occurs.