As of the time of this writing, the full set of Magic 2015 has been spoiled, including a blast from the past: the implacable Juggernaut! This creature has the ability to “attack each turn if able.” So what does “if able” really mean? First off, if there’s an effect that says it can’t attack at all, it can’t attack — so no circumventing summoning sickness and Pacifism. The next thing to note is that if an effect like Sphere of Safety says that it can’t attack unless you pay a cost, you’re allowed to attack, but you don’t have to — even if you could pay the cost, you’re not required to; and if you don’t pay the cost, Juggernaut isn’t able to attack.
Things get a bit more complicated once you throw other creatures into the mix. Let’s say you control Loyal Pegasus, who can’t attack or block alone, and a Traveling Philosopher. If Shipwreck Siren uses its ability to force Loyal Pegasus to attack, you’re required to attack with the Philosopher as well, since sending additional creatures into combat isn’t a cost that disqualifies the phrase “if able.” On the other hand, suppose you’re drafting Conspiracy and you’ve somehow picked up two Cogwork Trackers, but one of your opponents has a Silent Arbiter. In this case, you can’t fulfill both requirements at once, so you pick one and ignore the other. If both of your Trackers are required to attack different players, you’ll get to pick which opponent you’re required to attack this turn.
Today’s Rules Tip written by Jen Wong