Before rolling To Hit, nominate one of the Bastiladon'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 in the creature's rear arc.
Source: Warhammer Armies Project: Unofficial 9th Edition
Before rolling To Hit, nominate one of the Bastiladon'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 in the creature's rear arc.