Unzip & play. Only a windows build at the moment. If you die you have to manually restart the game.
The goal is to kill your enemies and attach their bodies to your eldrich horror. During battle you and your foe each preform one attack, alternating turns. Characters have 'Spirit' points and individual hit points for each body part. Either character dies if their "Spirit" points drop to zero. Attacks will generally damage the opponent's body parts, also doing equal damage to their spirit. Each bodypart has a unique skill associated with it. If a bodypart drops to zero HP, it is destroyed and the skill is unusable. Skills deal damage to specific bodyparts, random parts, all parts, or just spirit without damaging parts.
After victory in battle, you may perform a ritual to take your opponents body parts. (Sorry the tooltip is currently broken) Any parts in the "active parts" section will be the skills that determine your horror's HP and skills usable in battle. The "backup parts" are your inventory of replacements for future battles.
The general strategy is to try and kill your opponent without losing your bodyparts or fully destroying theirs (because then you couldn't attach it to yourself!). You almost always want to take and use parts from each foe as they get increasingly powerful. And be careful as parts decay as you use them - some more powerful parts decay greatly!