When this creature enters, you take the
initiativeThere are three inherent triggered abilities associated with having the initiative. These triggered abilities have no source and are controlled by the player who had the initiative at the time the abilities triggered. This is an exception to rule 113.8. The full text of these abilities are “At the beginning of the upkeep of the player who has the initiative, that player ventures into Undercity,” “Whenever one or more creatures a player controls deal combat damage to the player who has the initiative, the controller of those creatures takes the initiative,” and “Whenever a player takes the initiative, that player ventures into Undercity.” See rule 701.49, “Venture into the Dungeon.” (CR 726.2).
Whenever you
castTo cast a spell is to take it from the zone it’s in (usually the hand), put it on the stack, and pay its costs, so that it will eventually resolve and have its effect. A player may cast a spell if they have priority. See rule 601, “Casting Spells.”
To cast a card is to cast it as a spell. (CR 701.5) your second spell each turn, copy it. If you've completed a
dungeonA dungeon card is in the command zone while a player ventures through its rooms. (CR 309), copy that spell twice instead. You may choose new targets for the copies. (A copy of a permanent spell becomes a token.)