Very little about it is currently known. It appears to be generated by, or otherwise associated with, core-converted land. The environment within the L Barrier requires that Lilin take precautions, such as shielding themselves with Anti-L Hazmat Suits (対L結界防護服, tai-L kekkai bougofuku); however, metahumans such as pilots and Evas experience seemingly no ill effects from exposure. Inside the L Barrier, normal matter is corroded into core at a predictable rate, starting from the point of contact and creeping upward. L Barrier effects can be reversed at least temporarily by activating an Anti-L System, wherein at least one active sealing pillar generates a field of effect that seems to "hold back" the L Barrier.
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