Hi Eric,
We are trying to determine where this error is coming from. So since you have Java8 installed on your system already lets bypass our JVM by having you run the jar directly.
The following URL is a zip download of the Minion-jfx.jar and the required libs folder. Unzip the files and run the Minion-jfx.jar and see if it runs for you. If it doesnt please check if you have a .minion folder now and if you do please post the minion0.log.
http://cdn.mmoui.com/minion/Minion2.1.3pl1-beta.zip