In-Betweener

The In-Betweener is a powerful cosmic entity within Marvel comics and a creation of Master Order and Lord Chaos, designed to be a balancing force between the two eternally feuding entities - this means that the In-Betweener is officially a neutral entity but it has frequently delved into outright villainous acts, usually on a cosmic scale and as such is a dangerous and unpredictable force within the mainstream Marvel cosmic hierarchy.

Notable Events
The In-Betweener was created by Master Order and Lord Chaos to try and keep balance between the two concepts, however the entity has commited some very questionable deeds - such as a particularly malevolent plan to drive the universe into insanity.

Abilities
The In-Betweener is immensely powerful, having a direct link to both Master Order and Lord Chaos - putting him in the ranks of at least mid-tier "M-Body" class entities (commonly known as abstract entities) : he is not, however, on the same level of power as beings like Eternity, Death or multiversal entities such as Beyonder or Phoenix Force.

Trivia

 * The In-Betweener shares some very close similarities to the DC villain, Equinox.