In the first wave of "Morph" ice Changeling is the most stable of the 3 cards.
For its ress cost it is one strength lower then another 5 priced ice the Fire Wall, and has the same influence cost. For the purpose of taxing this makes changeling vastly inferior, unlike Fire Wall however this guy can change into a Sentry form, making him slightly more useful for actually ending runs when it matters.
Pros:
-Can become a 4 strength sentry that ends the run for a total cost of 6 and an extra click, a fair price compared to Guard.
-Not counterable with an unmodified Mimic. Some icebreaker suites may have to spend unreasonable to get through.
-Good target for Patch, locking out modified Mimics and becoming a respectable tax (6 to break on average) and very difficult to get through with stealth breakers. Just watch out for cutlery events.
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Cons:
-Bad tax in barrier form.
-Expensive.
-Only 1 routine for its price, bypassable with Femme Fatale or Knight fairly easily.
-Countered somewhat by AI breakers.
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Changeling shines in a strategy that focuses on denying the runner breakers, if you manage to kill a certain type of breaker Changeling has a good chance of being able to morph into that type and lock the runner out. Especially if you target sentries.