The rule at the time was you should play your cards as written, and as written, you could discard or mill a Rukh Egg and still get the 4/4 token, which led to the card being banned before Wizards eventually updated the wording
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This can be especially rewarding against players with death and taxes-style strategies, since their creatures are usually tools to push that strategy forward
I clearly wasnt alone in this line of thinking, because Black Market and Pawn of Ulamog saw an absolute ton of play during Commanders early years, and the former was actually a chase card for a while since its only printing was in Mercadian Masques prior to the release of Commander 2015
If you don't have a land in your opening hand, mulligan
This is less-versatile than the Sky Support Shaymin since you can only use one Trainer card per turn , but it's still a decent option