Contracted To A Summoner

"Any sufficiently advanced technology is indistinguishable from magic." - Arthur C Clarke

A veteran Force recon marine, isolated in the woods after tragically losing his squad and being discharged from the Marines due to his mental health, suddenly finds himself summoned to another world and contracted to a Summoner, a magic user with the power to summon and contract powerful allies to her side. Will he be able to stand toe to toe with powerful monsters and evil entities using only his significant stash of weapons and technology, or will he crumble under the might of this strange new world?