There are no requirements for this to happen, so the trainer can utilize this trump card at any moment they desire
On Turn 2 you draw your card for the turn, and play a Roseannes Research, getting a Baltoy GE and a Basic Energy card, meaning your deck is now 3 cards thinner at 43 cards
If you have Millicent and a Supreme Phantom on board, for example, you can target the lord with this, meaning the tokens youd get from your commander will be Spirit lords instead
But Urborg is different it's not itself a Swamp, it only has the word "Swamp" in its text description, which the official Commander rules point out is okay: Basic land words (swamp, forest, etc) in the text box of a card do NOT represent a coloured mana symbol
There is a reason why this card is the most well known card
This synchro monster has the ability to equip Magistus monsters from the extra deck to itself, and when it does, the opponent cannot summon monsters from the extra deck that are the same card type as the equipped monster
