He will pull out his maul and say, "I guess we're having some crab tonight," as he cracks down onto the head of the crab-like creature.
If the hit lands, he will divine smite that guy.
Rolls
Maul to hit vs crab thingy, bless, dmg - (1d20+1d4+6, 2d6+4)
1d20+1d4+6 : (16) + (1) + 6 = 23
2d6+4 : (14) + 4 = 9
Divine Smite dmg - (2d8)
(54) = 9
rerolling 1 on dmg die - (1d6)
(3) = 3