okay i will quote book before question
Ok , so if i understand it well. Bastilodon always have one attack at S10 ( even in front ) but only recives +1 to hit if someone is in the rear. Am i right?

Thunderous Bludgeon : Before rolling to Hit, nominate one of the Bastilodon's Attacks as the Thunderous Bludgeon (a different coloured dice works best). This Attack is resolved at Strength 10 and receives a +1 To Hit bonus against models inthe creature's rear arc.
Ok , so if i understand it well. Bastilodon always have one attack at S10 ( even in front ) but only recives +1 to hit if someone is in the rear. Am i right?