A SpookyJam 2021 Entry

Observed adds a new entity that watches and stalks players across the land. Inspired by Watchers from Barotrauma (Potential spoilers in link).
The shorthand explanation

A new entity, the Observer is added to this world. The observer doesn't attack the player, but only cares to observe what they are doing. Unfortunately, this observation remains quite harmful to players. As you are observed, you'll gain debuffs over time, faster if you are closer to an observer. Players being observed will also distribute the observing effects at half strength to nearby players

Interested? Here's some more!

The Observer makes a static-like noise when observing a player, making them easy to find and kill when they're observing a player.
Players will receive the observed potion effect to indicate their progression through the debuffs. The effect itself however does nothing. It is merely a visual indicator.
The observed effects will slowly go away over time, and are actively draining even while being observed.
The more observed a player is, the faster the observation points drain, and the more debuffs they will need to deal with until it drains.
Observers will drop a pool of potent poison behind them when attacked. Melee combat is not advised unless you are well above or below the observer.
Observers drop their eye on death, which can be eaten for quick food, with a short night vision effect being given upon eating. With a ghast tear this eye can also be turned into an eye of ender.
With Immortuos Calyx installed, eating the observer's eye gives a chance of infection, and individuals with the infection at 26% or higher will not gain further effects from being observed.

Can I put this in my modpacks?

Yes.

Commands added:

/observed setobservedlevel <Player> <0-100> - Sets the observed level of a given player.

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