The infinity gems have a physical form called nemesis!
The infinity gems turn into their physical form when the 7th infinity stone
is combined with the other six...
This 7th infinity stone is known as "ego" gem
The Ego Gem contains the consciousness of the cosmic entity Nemesis, which when united with the other gems reforms the character. This gem is found in the Ultraverse when the Asgardian god Loki attempts to steal the other gems. It has never been seen outside its initial appearance except for the Marvel Super Hero Squad: The Infinity Gauntlet video game and The Super Hero Squad Show where it is re-imagined as the Infinity Sword.
The 8th infinity stone is known as "Rhythm"
In the Marvel Super Hero Squad universe and related media, a seventh "Rhythm Gem" exists. The acquisition of the Infinity Gems is the main focus of The Super Hero Squad Show's second season as well as the Marvel Super Hero Squad: The Infinity Gauntlet video game. The Rhythm Gem was revealed to be a ploy made by Loki.