阿里阿德涅的线团/愛瑞雅妮的線球/Ariadne's Thread/アリアドネの糸 by IronPike
Ariadne fell in love at first sight, and helped him(Theseus) by giving him a sword and a ball of thread, so that he could find his way out of the Minotaur's labyrinth.
This mod can lead your way back to the location where you hit the activation key.
You can change the key in option menu. Default is P.
Do not need server support! You can use it even on a vanilla server.
In short, both. It's a ModLoader mod, but it works fine with Forge with no conflicts. Just tested it myself. The mod is also Clientside, so it'll work on servers even if the server host doesn't have it installed.
You should make an option menu with a distance choice... I mean when you activate the option the line only appear every... 2 or 3 block right? You should make it so that we can chose how many blocks we want before a new part of the line appear...