When chances of victory begin to look slim, a corrupted entity may exert the remaining amount of their energy all at once, contorting the host's body in the process.
This form is called 'Nexus'.
The corruption may harden and crystallize, making it better for
offensive capabilities at the cost of losing it's ability to infect others.
The Nexus form cannot be sustained for long, the corruption will begin to erode away as time passes in this state, making this similar to a last ditch effort.
In this form corrupting others is no longer the
objective, the only desire is
elimination.