u/BuckFlake

I have been researching this for awhile now and as soon as I feel like I get clarity, I get confused again. Please give me some slack as this is my first TCG but I know that the word 'when' is a trigger ability word and from my research cards like Brynhir can be a pain to play against, but I dont understand why. Apparently triggered abilities can be reacted to but this is where most of my confusion starts. Ive seen people say "It makes people use reactions at sub-optimal timing" and "its a trigger ability so it goes onto the chain' but whats confusing to me is I cant just play Brynhir when its not my turn or as a reaction to something so how does it add to the chain? Lets say this....Its now my turn and I have 6 runes available so I decide to play Brynhir exhausted to my base and then move my readied units to a battlefield to start a showdown. Now my opponent cant play a spell to increase/decrees a units might because I played Brynhir BUT could my opponent have played a reaction to stop Brynhirs triggered ability right as I played him because it has the word 'when' in it? I get that cards like ravenbloom student that say something like "when you play a spell I get a +1 might this turn" and your opponent counters your spell so ravenbloom doesnt get the +1 but things on the internet make it seem like a triggered ability can be countered and cards that start with the word 'when' have a trigger ability. Any help is appreciated and if you could provide real world examples down below that would really help my peanut brain. Thanks!