You may reveal this card from your opening hand. If you do, when each opponent casts their first spell of the game, counter that spell unless that player pays.
Whenever an opponent casts a spell, counter it unless that player pays.
6/1/2011 If you reveal more than one Chancellor of the Annex from your opening hand, each will trigger when an opponent casts their first spell of the game. That player will have to pay that many times or the spell will be countered.
6/1/2011 In a multiplayer game, if you reveal Chancellor of the Annex from your opening hand, it will trigger each time an opponent casts their first spell of the game.
6/8/2016 A player’s “opening hand” is the hand of cards the player has after all players have taken mulligans and “scryed” if applicable. If players have any cards in hand that allow actions to be taken with them from a player’s opening hand, the starting player takes all such actions first in any order, followed by each other player in turn order. Then the first turn begins.