What is that word that sounds like "assent" in No Game No Life? In the TV animation of No Game No Life, before every game, the players who join the game would shout out loud a word that sounds like "assent". I once thought it was assent, as the story make it seems like it is saying "I agree with the game contract under the 10 rules" (where the subtitles says the word means "swear under the 10 rules", which sounds no contradiction with the word "assent"). 

Until I watch the new movie No Game No Life Zero, which tells the story of where the creating of the game world we see in the TV animation.

In the movie, when the man sacrifice himself to let Riku runs away, he shouts a word that sounds like "assent". I thought, so this is the origin of the word, but I was wrong. When later Riku and the ghosts started their plan to finish the war, Riku corrects their pronunciation. According to the subtitles, the meaning was changing from "swear to the former brave" to "swear to the rules", but both words to me still sounds like "assent".

So what actually were those words they were shouting?

P.S. I was watching the movie in Hong Kong and the subtitles are in Traditional Chinese. The subtitle decided to show the meaning instead of putting the actual word in it.
The only word that closely resembles the word you're asking for is "Aschente". It's pronounced more or less like: "A-shen-te".

It means one pledges to the ten 'rules' made, and placed by the one true god Tet of Disboard. They state it at the start of every game that uses the ten rules.

(I've linked more about the ten pledges and such in the link above)