Post's Citadel - Bolas's Citadel [Secret Lair Drop Series] 144 A player must announce when

A player must announce when one of their floaties has been completely discovered and remove the tile from the game board

"At the outset

{T}: Put a mire counter on target non-Swamp land

you’ll need to lay the tracks

Post's Citadel - Bolas's Citadel [Secret Lair Drop Series] 144 A player must announce whenSet: Secret Lair Drop Series Type: Legendary Artifact Rarity: Rare Cost: {3}{B}{B}{B} You may look at the top card of your library any time. You may play lands and cast spells from the top of your library. If you cast a spell this way, pay life equal to its mana value rather than pay its mana cost. {T}, Sacrifice ten nonland permanents: Each opponent loses 10 life.