I have a question that I seem to get varying answers on. A friend of mine plays a "Everything you can do, I can do better" deck that's all about copying other people's creatures multiple times over until he has a big army of your creatures. So let's say he has a Followed Footsteps enchanted onto a Clone that's a copy of Jhessian Infiltrator, on the upkeep trigger for Followed Footsteps, will he make a token of the Jhessian Infiltrator, or will he get a token of the Clone, free to copy something else (say Doomed Deserter or Phyrexian Hulk)? Different people say different things about what to do in that case and he seems to change how that happens each game.
Entirely unrelated to the infinite mana combo, another cool combo with myr, that can potentially be a turn one win, is Myr Retriever + Myr Retriever + Heartless Summoning + Altar of the Brood. Or, the same thing but with Impact Tremors instead of Altar of the Brood.
Heartless Summoning allows you to play one Myr Retriever for free, triggering either Impact Tremors or Altar of the Brood; however, it'll die immediately. Then, you play your second Myr Retriever, triggering either Impact Tremors or Altar of the Brood again, allowing you to return the first Myr Retriever from your graveyard to your hand; however, the second Myr Retriever will also die instantly. Now, just continue between playing and returning the Myr Retrievers for free until Impact Tremors kills or Altar of the Brood mills.
Mortivore would be pretty good, as long as it has a stable power and toughness before setting off the chain, it will be extremely buffed at the end of the chain. The only problem would be that a lot of graveyard return will only weaken it, particularly something like Grave Betrayal, pulling your opponents dead creatures onto your side will mean that the Mortivore won't get the power and toughness boost from a creature being in a graveyard while still giving it the consecutive -1/-1 from those creatures dying. Overall meaning that if you aren't careful you could easily kill one of your potential late game powerhouse/win-cons.
Heartless Summoning allows you to play one Myr Retriever for free, triggering either Impact Tremors or Altar of the Brood; however, it'll die immediately. Then, you play your second Myr Retriever, triggering either Impact Tremors or Altar of the Brood again, allowing you to return the first Myr Retriever from your graveyard to your hand; however, the second Myr Retriever will also die instantly. Now, just continue between playing and returning the Myr Retrievers for free until Impact Tremors kills or Altar of the Brood mills.