To clear some of the confusion for the people that asked if Sentinels are allowed to play in Masters 3 because they are already qualified for Champions. It doesn't matter. It's still circuit points, points that they can steal from another team/from another region, which may change the circuit points standings for champions, and of course, prize money. They are qualified because of the way circuit points possible scenarios are, it doesn't matter if any other NA team gets the points in Berlin, they are guaranteed to qualify.
They already qualified based on circuit points because in no scenario, any other NA team that would get the remaining circuit points would be able to drop them down from the 1st or 2nd slot in NA circuit points ranking, and the only team that has a scenario that drops them to 2nd place is V1.
Let's say V1 gets the 375 from 2nd place Berlin, that will put them at 575 points, which will be above SEN, but even so, SEN would still be 2nd in NA points and qualify because no other NA team that would get the remaining points would be able to pass SEN that has 500. 2nd place in Berlin gets 375 points, and even in the scenario of Envy getting them (currently 3rd in circuit points NA), that would be 460 which is still less than Sen.
Example in which Sen wouldn't have qualified for champions right after winning Iceland: if Envy won Masters 1 and had the 100 points to put them at 185, Sentinels (I am not counting the points they may have gotten from other places in Masters 1 because it's just an example, let's say they lost, and they would only have 400 points) wouldn't have had the spot guaranteed because both V1 and Envy had a chance to get the first 2 spots in the circuit rankings (in fact any other team that would be able to finish with more than 400 points pretty much), but as it stands, Sentinels are guaranteed 1st rank in circuit points in NA under any scenario from any NA team that would make it to Berlin except for V1. In other words, the only team that can "hurt" Sentinels is V1, but even if they could, they can only drop them to 2nd place in NA circuit points ranking, which still qualifies them (just an example, applies to more teams in the scenario in which V1 would secure 1st rank in circuit points)
So Sentinels are qualified because all the possible scenarios regarding the qualifying methods secures their spot no matter what, at least via the circuit points rank. There's also the possibility of winning Berlin which, I think, just favors the region by getting another team in champions via the circuit points ranking.