When can Sett Brawler's ability be used, and can counterspells target unit abilities?

Ruling: Sett Brawler's ability can only be used during your turn when there is no chain present and outside of a Showdown. Counterspells cannot counter unit abilities unless the counterspell specifically states it can counter abilities.

Sequence:

• Must be your turn
• No chain can be present
• Must be outside of a Showdown

Nuances:

• The ability is base speed
• While the ability behaves like a spell once activated, counterspells need to specifically state they can counter abilities to target them