Trophy description - Destroy 10 consecutive Sentinels before they escape in Survival mode

Trophy - Silver

Sentinels are the large spiked enemies that explode when killed, similar to your own bombs, and have an HP bar. As you progress they will gain more and more HP, as well as becoming more difficult and shooting many bullets in a circular motion.

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There are 2-3 per "day" so if you focus on killing them when they appear, this should come by the 4th or 5th day. Note: The game will not notify you via a prompt when Sentinels appear, but there WILL be a fairly noticeable health bar at the bottom of the screen, so keep an eye out for that.

If the game tells you that a bridge has been destroyed and you did not recently kill one of these, then you missed one.