The majority of the dog is yellow, with green legs and a bright purple tail. All four legs turn at the hip/shoulder and the tail, which splits in two, bends at it's base. Sadly there's no motion at all in the necks or the heads. On his back, like his fellow Terrorcon Rippersnapper, there is a 5mm peg hole on which can be mounted his beast mode weapon, a flame gun. The robot's arm run under the body of the beast which allows his robot mode gun, an armour-piercing rocket-grenade launcher, to be stored in beast mode.
Transformation: Remove the beast cannon. Fold the heads back and the tails forward. Pull the body apart and stand on the rear of the toy. Fold the legs back behind the toy. Fold the arms up. Put the robot mode gun in the robot's hand.
Sinnertwin's robot mode is predominantly yellow again, with the green serving as the upper legs, arms, chest centre and head. He's got the same short arms as Rippersnapper with just a joint attaching them to the body as the robot's sole articulation which makes the arms look as if they're attached to the body by the elbow. Sinnertwin possesses possibly my favourite transformer handgun. His green armour-piercing rocket-grenade launcher has two barrels mounted on top of each other surrounded by a rounded off casing. It's a lovely looking sci fi type gun.
Sinnertwin has a bonus Centaur mode: From robot mode retract the robot legs and fold the rear beast legs down for him to stand on.
As with the other Terrorcons, Sinnertwin forms part of Abominus.
Arm mode: Take the beast mode, fold the rear legs forward along the side of the body and fold the front legs up and back to sit on top of them. Lift the heads & necks up and fold the robot head down to form the connector - this is harder than it sounds because the slot for the connector peg in the middle of the chest is slightly too small. Fold the tail up and insert a fist into Sinnertwin's bottom. This mode allows Sinnertwin to continue to mount his beast gun which thus forms a shoulder cannon for Abominus
Leg mode: Take the beast mode, remove the gun, fold the rear legs forward along the side of the body and fold the front legs up and back to sit on top of them. Fold the heads & necks back and the tail forward. Insert a foot into his bottom.
Overall: A fab beast mode makes the toy, but the design limitations in 1987 make it easy to confuse Sinnertwin's beast type with the similar looking Hun-grrr.
Sinnertwin was sold in the US & UK in 1987 as Terrorcon TR-2. He was sold in Japan as Transformers toy D-81 where he was also part of the D-84 Abominus giftset.
Sinnertwin has never been reissued or recoloured.