Zxygo's Crystal Util

The mod works out how much damage a nearby end crystal would deal by reading its height above or below the player and its distance from the player. From those values it colors an on-screen indicator to match, from green for the least damage up to red for heavy damage. Intermediate positions blend between the colors, so a crystal above and far away shows green while one close and low shows a stronger shade.

The indicator can be toggled on or off at any time. The author describes the mod as a first release that may still contain bugs, and presents it as a learning tool for players starting out in Crystal PVP. It is not meant for cheating: the author states that it does not support hacking of any kind, and reports of it being used to gain an unfair advantage on some servers are noted as misuse. Its performance impact is described as minimal, and it works in multiplayer.

Crystal Util requires Fabric and runs only on the client, so servers do not need it. It is published for Fabric across 3 release versions, 1.21 – 1.21.4, under the MIT License, which is not open source. Simple Mod Menu Integration is listed as a companion for its settings.