- Allowed some cards to be selected as commanders even if they are not legal. They deck will still be marked illegal but at least you can select them. This is to allow flexible "Rule 0" decks with Un-set cards, banned commanders and stuff like Princess Twilight Sparkle. I thought about adding a separate format - something like "Commander (Relaxed / 'Rule 0')" - but it feels hacky and unintuitive if you don't already know what it is and what it's for.
- added the Duel Commander format
- fixed Hornet Queen rarity (MythicRare -> Rare)
- imported D&D: Honor Among Thieves Universes Within promos

you could make any card selectable as commander and notify user about illegality somehow eg show them as illegal in legality popup. that might be least confusing from user pov. off-by-default checkbox, like the one for pulling card from inventory, to enable this would ensure legacy functionality is untouched without explicit user wish.

I noticed that with the Universes Within cards you can have both the Universes Within version and the D&D: Honor Among Thieves version in a Commander Deck without the system warning you that you can only have one copy in your deck. Since you are not allowed to have two versions of the same card in the same Commander Deck, it would be nice to see the warning. It seems the same problem is happening with all the Universes Within cards on deckbox.

While this only affects a few cards at the moment, with the Spider-Man Through the Omenpaths set coming out soon, it could end up being a big problem in the future for building decks on deckbox.

As always, thanks for your hard work.