As promised here is the blog covering the Chancellor cycle.
Each colour has its own chancellor, a powerful member of the Phyrexian hierarchy. Each are 7 mana creatures that can have an impact on the game before it's even begun. For example:
Normally, you wouldn't want a 7 mana creature in your opening hand. Chancellor of the Dross, however, can put you onto 23 life and your opponent on 17 before the game even gets going and that's if you've only got one opponent!
So what happens if both players have chancellors or one player takes a mulligan?
I win the roll and opt to play first. I then take my opening hand of 7 cards, two of which are:
I don't reveal it yet, however, because my opponent may wish to mulligan. They look at their opening hand which contains another chancellor but decide it isn't worth keeping. If a player mulligans, the hand they initially drew does not count as their opening hand and therefore the Chancellor is not revealed.
My opponent then draws a new hand of 6 cards, which they keep. As I'm the active player, I reveal my two chancellors in the order of my choosing (in this case I would reveal Spires last). Both abilities go on the stack with the last revealed on top.
Then my opponent reveals:
As Chancellor of the Forge was revealed last, its ability will go on the stack and resolve first.
1. My opponent gets a 1/1 red Goblin creature token with haste in my upkeep step as it is the first upkeep of the game
2. Chancellor of the Spires ability resolves and my opponent puts the top seven cards of their library into their graveyard
3. The ability from Chancellor of the Annex resolves resulting in a static effect which means the first spell my opponent casts is cancelled unless they pay 1 mana
I hope this has helped clarify any issues which arose from this cycle of cards.