There are combos you cannot perform that are in accordance to Magic's rules, related to
Krark-Clan Ironworks.
There is a combo that involves sacrificing 2 or more artifacts to pay the cost of a spell. What happens, currently, is that you can't simultaneously sacrifice multiple artifacts. They are individually sacrificed, even if you can pay the cost by sacrificing multiple. They need to happen simultaneously. This is according to the rules. The combo is as follows:
You have
Krark-Clan Ironworks,
Scrap Trawler and
Myr Retriever on the battlefield, a
Chromatic Star on the graveyard and a 1 mana cost artifact in your hand that you're casting. To pay for that cost, you sacrifice both
Scrap Trawler and
Myr Retriever and pay 1 mana for that spell to resolve, meaning you have 3 mana on the pool. You get a trigger from
Myr Retriever going to the graveyard from
Scrap Trawler, from
Myr Retriever itself and you get a trigger from
Scrap Trawler going to the graveyard. You resolve those triggers and you get
Scrap Trawler back,
Myr Retriever and the
Chromatic Star. You sacrifice the 1 mana cost artifact you played before and you have 5 mana. You play
Myr Retriever and
Scrap Trawler and spend all that mana. You play the
Chromatic Star, and to pay the costs of that spell, you sacrifice both
Scrap Trawler and
Myr Retriever again. You get both back and the other 1 cost artifact from the graveyard back. You do this over and over again for infinite draws.
You can't perform this very important combo on xmage.