In the backwaters of the Merrow Lanes lie stones scarred with tallies of countless generations, each representing a victory of merrow soldiers.

Veteran of the Depths

Whenever this creature becomes tapped, you may put a +1/+1 counter on it.

The List

Lorwyn

Whenever Veteran of the Depths becomes tapped, you may put a +1/+1 counter on it.

For the ability to trigger, the creature has to actually change from untapped to tapped. If an effect attempts to tap the creature, but it was already tapped at the time, this ability won’t trigger.

This is a triggered ability, not an activated ability. It doesn’t allow you to tap the creature whenever you want; rather, you need some other way of tapping it, such as by attacking with the creature.