In Power Rangers, there was a character, he wore full black body armour, horns, a black cape,continues...?

Question

and an octagon on his chest which i beleive was the only way he could be harmed, he was evil, but then turned good and i beleive died. i cannot remember his name or the season in which it happened. i had to rephrase my last question due to some misleading information.

Answer 1

The was the Magna Defender from Lost Galaxy, Mike Corbett's spirit was captured inside after Mike fell into a crevass caused by Furio's sword, then when Mike was ejected from him, he became Magna Defender.

Answer 2

Could be one of these...

http://en.wikipedia.org/wiki/Other_Rangers_and_Ranger-like_allies