Cause it's mandatory, so it...like just has to happen.

I say we D Prison/Smash/Spin/any other kind of effect removal that sucker and then chain Oppression to its effect so we won't have to deal with it in the first place. Do kids still play with mandatory effects that activate simultaneously with another effect as the last things to resolve in a chain?

How did I miss this. Trish does chain to tengu. Mandatory effects will wait for the first chance to legally activate. They cannot initiate a chain in the summon negation window as they do not negate a summon and they cannot chain to something that can negate a summon as they are spell speed 1 so they wait for the summon response window to activate. When you summon Trishula, during the summon response window, where you can legally activate any spell speed 2 as well, Tengu will activate and Trishula will activate as well since that's where it triggers. As Tengu Triggered first he goes on chain Link 1 in the TCG (its mandatory too so it wouldnt matter in the OCG either) and then Trishula will occupy chain Link 2. Royal Oppression is another matter as it has to do with the summon negation window.

Well when you said respond to a summon you could be meaning summon negation where of course Tengu does not activate, but on the actual summon response window it does, and chains with whatever trigger effects are there, similar to the BRD-Dandylion combo, meaning the guy said nothing wrong about his chain (except from using the word "activate" instead of "resolve" ofc). You can use Royal Oppression in the summon negation window for trishula of course but on the summon response window yes, trishula will stop you from chaining royal oppression to tengu. Now as to why you chose to negate Tengu and not hte Trishula I don't know, debunk perhaps? That also means you wouldnt have priority to use Brionac's effect in this case as Tengu will force himself on chain link 1 and Brionac cannot chain to anything, so he is BTH-able before he can activate.

I understand it like this: Mandatory effects(don't have "can" and other words like that in the effect) WILL happen, meaning imo is the timing would somehow be missed under normal circumstances, the effect will activate after the previous one resolves. I got it from this example: Naturia cliff is tributed for Caius, now I beleive Caius will activate but cliff will NOT, just cuz the last thing to happen was the summon of caius and not cliff being sent to grave, hence the timing is missed, It all depends on the wording of the card, but for me, in order for it to not miss the timing, the conditions of the card effect must be the direct last thing to happen(unless the effect is mandatory in which case it will happen no matter what you do)

Actually it's not only about mandatory. The only things that can miss the timing are "when..., you can" optional trigger effects. The "when" denotes time, it will activate "when" its trigger is met, not at another time, if "when" they were supposed to activate it was impossible to build a chain due to the game rules (while performing a summon, while resolving a chain etc.) then they miss the timing and miss their chance to activate, unless it is mandatory at which case it persists as we said here and will wait until the first chance to activate.

But there are also "if..., you can" optional trigger effects. These do not care if the timing is missed, they will activate "if" their trigger is met, and not "when" it is met, so they act like mandatory effects, they will wait and will activate at the time a mandatory effect would, whether they are optional or mandatory effects themselves. For example the scrap effects are optionals, but they have "if" so they dont care about timing, that's why chaining scrapstorm still works with them.

In the end missing the timing is quite a simple thing so long as you don't try to slap the term in everything you don't understand due to lack of knowledge. If a "when..., you can" optional trigger/trigger-like effect meets its trigger at a time you cannot build a chain immidiatelly and as a result when you can activate an effect it meeting its trigger was not the last thing to happen, then it has missed the timing and you cannot activate it. Missing the timing is that and only that, not when call of the haunted is chain link 2 when you have bottomless and not when you chose to let attack declaration go and decided to use your dimensional prison now. It is only the above.

^ What the guy said.