Auriok Siege Sled

Both activated abilities point outward at other artifact creatures, which is the whole oddity here: this is a Juggernaut that manipulates the combat math of the artifact mirror rather than its own. Pay one and an opposing artifact blocker is forced into the path; pay one and a different one is barred from getting in the way. With several metal bodies on the table, that means dictating exactly which one trades into a 3/5 and which one stands aside, opening lethal lanes for whatever else is attacking alongside it. The catch is that both clauses only read artifact creatures, so against a non-artifact board the sled does nothing but attack as a plain six-mana 3/5. That narrowness is the design point: this came out of an era built around an artifact-saturated world, where several cards assume the opposing side is also made of metal. Read against that backdrop the abilities are a control valve for a board state the set expected you to be in, not a generic combat trick. The five toughness matters too, since it survives the kind of pings and small blockers that punish glass-cannon attackers, letting the sled keep swinging turn after turn while it reshapes who can answer it. A creature that is most interesting not when it attacks, but when it tells the other artifacts how they are allowed to behave.