Crusty Hammer is the boss from zones P, R and T from Darius Gaiden. In Darius Gaiden Extra Version he is the first boss in the game. It is shaped after a mantis shrimp.
Crusty Hammer uses similar patterns on the three zones where it appears, with the properties of its attacks changing between them. After making his entrance, he will rear back and forth for a while, then shoot lasers at the player. After this he will curl up and spin while shooting lasers/bullets all over the screen or attempt to charge at the player, leaving the screen. He will attempt to crush the player upon returning. Whenever he is curled up his body will deflect the player's shots.
On his next attack, Crusty Hammer will stand straight and follow the player's movement, after which he will swing his arm to hit the player, then shoot lasers at the player. He will do this two to three times before resuming his pattern. He will once again rear, then shoot various lasers over the screen. If he's taken enough damage, his previous attacks will become more aggressive and he will also use a few new ones. He will curl up then start floating while shooting lasers all over the place, drop orbs which burst into bullets, shoot bullets and heat-seeking missiles while moving and swing its tail while shooting lasers.