Unless the opponent has whiffed hard, they should have something in hand to stop it, as theyll have had the chance to prep plenty of lands in the time it takes to get the resources to play Jumbo Cactuar
As another example, if at the start of turn six you have five cards in your inkwell and hold a two-drop, a three-drop, and a five-drop, then just cast your five-drop and dont add anything else to the inkwell at this point
But since its a blue Wizard, I decided to test it in a Flame of Anor shell with Moxen and Baubles
Sapphire Medallion can be particularly strong in multiples, building towards a Capsize-lock endgame (bouncing two or more lands a turn on their end step to keep forward progress going without risking anything)
These cards offer an initial boost or ability, but can then be upgraded using mana up to level three