At the beginning of your upkeep, look at the top card of your library. You may reveal that card. If an instant or sorcery card is revealed this way, transform Delver of Secrets.

Commander creatures you own have "Room abilities of dungeons you own trigger an additional time."

Cave Entrance — Scry 1. (Leads to: Goblin Lair, Mine Tunnels)

Goblin Lair — Create a 1/1 red Goblin creature token. (Leads to: Storeroom, Dark Pool)

Mine Tunnels — Create a Treasure token. (Leads to: Dark Pool, Fungi Cavern)

Storeroom — Put a +1/+1 counter on target creature. (Leads to: Temple of Dumathoin)

Dark Pool — Each opponent loses 1 life and you gain 1 life. (Leads to: Temple of Dumathoin)

Fungi Cavern — Target creature gets -4/-0 until your next turn. (Leads to: Temple of Dumathoin)

Temple of Dumathoin — Draw a card.