It's a solid plan: you have an offensive strategy and a defensive fallback position. If you succeed in either area, you'll have scored a significant victory against the Surgeons.
The best way to sow destruction among the Surgeons would be to open the flask on the other side of the portal, before they come through. Of course, Katariki's mark on your shoulder means that you're likely the only person present with the power to pass through the portal.
Through experimentation, and with a little help from your research department, you're beginning to get an inkling of how to use the Zapp Sapper. You may be able to drain the portal's power from this side, but a more effective strategy would be to access whatever apparatus the Surgeons use to generate their spatial conduit—and that will be on the other side of the portal as well.
Of course, should Katariki show up, he also possesses the ability to traverse the Surgeons' portal.
In any case, you decide to hold on to the Zapp Sapper and the jinn flask yourself, for now.
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