Terrablox

A 3D voxel virtual tabletop (VTT).
A VTT is a shared virtual table for running tabletop RPGs (or other similar tabletop games). The GM builds the map out of blocks, drops in tokens for the party and monsters, then runs the session: moving tokens, revealing fog of war, rolling dice, chatting with players - same as you would at a physical table. Terrablox doesn't have its own rules or content; you bring your own game.
Building is fast and easy, like drawing pixels but in 3D. Left-click to paint, drag to fill a wall or a variety of shapes like ramps, pyramids, hills and more. Copy any chunk of your scene and paste it elsewhere, or share it as a text string in your notes (inspired by Talespire "slabs"). You can convert sections of the level into "props" that can be moved and rotated like tokens. Because voxels are abstract blocks, they can be used to build in any genre from fantasy to modern to sci-fi.
Once the map's built, that's when the session actually starts: the GM and players move their tokens around, reveal or hide the map with fog of war, roll dice in chat, and players see only what their characters would see.
Multiplayer is peer-to-peer: the GM hosts and players connect directly, over LAN or online via Steam. No server to set up.
Fog of war is fully 3D. Areas your party has visited can stay visible behind partial fog. Visibility is team based, so your players can share vision, have individual vision, or you could run PvP wargames with fog of war tracking multiple teams.
Lighting is raytraced through the voxel grid: sunlight, ambient occlusion, colored lighting, emissive blocks, and more.
Tokens are built as "standees" from any imported image, and can be scaled to any size, so custom characters and monsters are easy to import. Tokens can store notes, and can optionally be set up with custom stats like HP, status effects, etc.
Current features:
Build voxels with a variety of 3D shape tools like rectangles, cylinders, ramps, pyramids, etc.

Fog of war / line of sight

Shared or private vision; each team has its own vision and exploration

Players can be granted permission to get vision from and/or move tokens

Players can be assigned to any combination of teams

Build voxels in any color, make them transparent, emit light, and/or non-solid

Copy & paste sections of blocks and save them to a prefab library - pastes can be rotated, flipped, and scaled

Import Magicavoxel files

Import images with optional heightmaps and place them into scenes for reference, or convert them directly into voxels

Import any image as a custom standee token. Standees can be any size, can emit light, and be toggled as flying, ridable mounts, and more

Alternate camera modes like isometric, top-down, or first-person from a token's perspective

Set custom units for rulers, so blocks can represent 1 foot, 1 meter, 1 mile, or whatever else works for the scene.

Voxel-based lighting from a directional sun, ambient skylight, basic ambient light, and light-emitting blocks

Convert selections of blocks into "props" that can be moved around and rotated like tokens - use for doors, furniture, vehicles, etc.

Dice roller in chat, using Roll20-style syntax (exploding dice, keep/drop, etc.)

Turn tracker for initiative-based or real-time play

GM and player notes, stored locally in the campaign as text files