A dark side power resembling fiery energy was used by Darth Sidious to attack Ezra Bridger and Ahsoka Tano. Manifesting initially as fire, it served as both a weapon and a tool in order to bind and draw someone closer, as it did with Ezra. This physical manifestation formed a connection between the two, allowing Sidious temporary access into the World Between Worlds. The manifestation was akin to a tangible rope. The energy was conjured via the use of a Sith ritual altar.
The energy could also be blocked by someone powerful in the ways of the Force, as shown by Tano during her confrontation with Sidious. The process proved extremely taxing on her however, and she was left exhausted as a result. Any physical manifestations could also be severed with the use of a lightsaber, as was the case when Ahsoka used her lightsabers to cut the energy wrapped around Ezra's leg, severing the connection and causing significant pain to Sidious in the process.