These are the ones that are an ability on a permanent, usually a creature, that allow you to activate the ability to execute your counter magic
Usually, the answer is commander damage or sending them back to the Stone Age
Now that you understand what is a triggered ability in MTG and how the different types work, you can spot these effects on cards and plan around them
If you untap and play an Elvish Archdruid, you're going to much rather have that Cylian Elf on the battlefield
Make sure your opening hand has green mana production in it, because you will need it
All the new cards weve made we considered for a future in Commander [a Magic format in which your deck features a legendary creature], rather than to impact on our high-level competitive play