Germ

Germ is an exclusively black creature type with base power and toughness of 0, which only appears on tokens.

History
Germs were introduced in Mirrodin Besieged and represent phyrexian microorganisms carrying Phyresis. They are essentially analogous to the newts of Old Phyrexia.

Germs are created by living weapons when they enter the battlefield, which the living weapon automatically attaches to. Thus, living weapons are themselves creatures until they die or their controller chooses to equip the living weapon to a different creature. Detaching of the equipment will normally kill the Germ, as it would then be a 0/0 creature.

Grip of Phyresis is a blue instant featured in Commander 2016 that also makes use of this technique.

With the release of Modern Horizons 2, Germ tokens became Phyrexian Germ tokens instead. All effects that create Germ tokens received errata to instead create Phyrexian Germ tokens.