Communicating the idea of danger to an unknown alien civilization

An alien automatic "beacon" tries to warn us about some imminent danger. It does so with launching a succession of large "veils" in front of their star so we can detect them via the transit method. This succession of dips in the star luminosity forms a binary message.
The first part of the message conveys some cosmological and mathematical constants so we can agree on a set of SI units and know which branch of physics we should stop tamper with.

And here comes the second part of the message, the one wich actively tries to warn us of some danger. No need to be explicit, a simple "DANGER" sign would be sufficient. The problem is, the beacon doesn't know us. It knows our relative position (and maybe can scan our solar system as a whole), that we're a rather intelligent species having tinkered with the wrong physics, but that's about it.
The aliens don't know our language, our appearance, or even what biological process Earth's lifeforms are based on (or maybe just that we're carbon-based). They can't wait for a response and subsequent dialog to slowly build up comprehension: the message should be clear : "YOU ARE IN DANGER".
Also, please note that their goal is to eventually make us come to them for a solution, so no "warning shots" strategy. They must not be considered as the danger themselves.

In short:
How would aliens convey the sense of danger without knowing us beforehand ?

A bit of context:
- The aliens are about 40 light years from us
- The setting is 150 years from now, but they don't know our exact technological advancement (only that we should probably have colonized our own star system and are able to pick up their message)
- No FTL
- The shorter the message, the better (they don't have an infinite supply of stellar veils)
- The danger in question is of lovecraftian nature, and as such can't be properly explained with such "low bandwidth", hence the more universal danger sign sought after.

posted over 4 years ago

Keelhaul‭

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