Shadow is an underused piece of ICE. In faction tagging is extremely good for Weyland, but that comes on the price of it being ICE - Subroutines rarely fire more than once, and certainly not a second time without the runner being prepared for it to do so. Shadow however, is advanceable. This means that even if the runner isn’t going to hit it, they may not be able to run it if they don’t want the tag. Runner is using Mimic as their primary killer? Then triple advanced and this card means the runner now has to deal with a trace five (From the free two credits) to avoid a tag, or waste a click every time they want to run through it. A Builder in front of it can suddenly put it out of the runner’s reach to break, and of course Corporate Troubleshooter can really put the subroutines back into effect.
Still, tags from ICE are harder to land, more often needing on encounter effects (Data Raven) or simply being that it is more effective to take the tag and clear it afterward, for being too expensive to avoid in the first place (Gutenberg). Shadow is however, in faction for one of the most potent forms of tag punishment, and that makes it dangerous - if underused.
(Written as Chrome City was just released . )