Doomtrain
Poison Elemental
Doomtrain is effectively a train that casts a variety of status ailments onto your enemies. His auto-shell is very useful as is the defences he provides against magic and status attacks.
Pick up the Solomons Ring from Tears Point in Esthar. To use the ring you need to collect six Steel pipes, six Marlbro Tentacles and six Remedy +. Remedy +'s can be created using Alexander's Med LV Up skill on normal remedies. Once all these items have been found use the ring and Doomtrain will be yours.