Dream wore a hidden smirk underneath his mask as the rest of the members of the SMP trapped him in the so-called inescapable Pandora's Vault. The thing was, it may not look like it but there were at least two ways for him to escape.
And both of them were accessible to him, he had a team, some people who owed him favors and/or some people who were still loyal to him even though he was incredibly shitty, and there was a way to escape without them too.
(Well, not really him, but still a part of him, if you get what he meant.)
Not that he was going to escape, of course. He intended on staying there for as long as he could, even if it costed him his freedom and his friends.
It was all to protect them. Protect his friends, his family and his supposed "enemy," TommyInnit.
It was all worth it, as long as everyone was going to be safe.
Even if Nightmare was going to give him hell for it later...