Shield
The Holtzman energy field worn as personal armour across the Imperium, which is why its soldiers fight with blades, and which cannot be worn long on Arrakis.
A shield, sometimes called a Holtzman shield, is a protective energy field thrown around whatever it is meant to protect. A Holtzman generator produces it, and it can be calibrated to admit matter travelling below a set speed. Because shields are everywhere, firearms and directed-energy weapons became largely obsolete or too dangerous to use, so fighting went back to blades and precise technique, and anyone of the slightest importance wears a body shield. The danger is in the interaction: a lasgun beam striking a Holtzman field sets off sub-atomic fusion and a nuclear explosion, and whether it goes off at the shield, at the gun, or both is a matter of chance.
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