I've just realized this, but Sir Constantine is white... and that gives me a very bad feeling. I won't spoil anyone as to why... but suddenly I'm dreading things a lot...
As for who destroyed it, I'd assume War. Sir Constantine was likely there, and shamed or not, he's still a Royal Knight. The Peacemakers are likely the only Digimon on the planet otherwise who can claim to have overcome him, and even then it took Svarog, who's among our strongest. So either Mephistopheles himself did it, or War did, or some servant of equal power we have yet to encounter.
As for Chess Kingdom, oppression, fear, Chessmon. It's the Red Chessmon in charge, now who does that remind everyone of? Armed revolution, the former rulers executed... this is sounding very familiar...
I pity Thor if he tries to stop Tiwaz from taking charge. Unless he knows Tiwaz's secret weakness... that is...