Context: For a new Underrail Campaign
Type: Mechanics change
Idea: Characters have a hitpoint reserve. This reserve is drawn upon by healing and other abilities.
Expansion: When the reserve is depleted healing items function at a reduced effectiveness. New interactions allow for characters to escape death in a economic manner (as opposed to through random number generation) by drawing upon their hitpoint reserve (alternative to a tabletop 'character save') and provide a resource to be spent by feats (thick skull, last stand) that would benefit from incremental limits on use.
Specific usage: Characters of note (Player character, plot critical characters (Tanner), storied characters (Gorsky, Rathound King, Balor) and challenge characters (Tchort) could be given a feat that allows them to make a check (dependent on Will, potentially constitution at half rate, perhaps some kind of skill 'Toughness' at a tenth rate) to spend hitpoint reserve to cancel out killing damage, equal to twice the damage points (or at whatever rate is best) that would reduce a character below one hit point.
In gameplay terms, these characters would take a certain amount of assured damage and then start taking an variable amount after that based on their hit point reserve and success at rolling to avoid death, dependent largely on their statline, skills and feats.
