I don't understand how people can compare caribou's swamp element and BB's yami yami.caribou has shown that he can also store few things in his swamp like body but a swamp can't store df abilities or attacks .I think caribou's body itself acts as whole new dimension within itself .Remember Fullmetal alchemist brotherhood glutonny .he eats everything and everything he eats goes within is body which itself was a new dimension .Caribou's power is similar to that .cause He can store objects bigger than himself ,greater in number within is body.This is possible only when his body itself acts as another dimension.His power is similar to capone .Capone's body itself acts entirely a new dimension where he can store his subordinates .
On the other hand BB's Df is unique.It doesn't turn himself into darkness or gravity(whatever u can call) but rather he can control gravity or darkness.A person who can control gravity can easily connect alternate universes cause gravity is the key.
Remember his body is not a separate dimension like caribou's but his ability can absorb everything into an alternate dimension .
