I've been enjoying reading the compact excellence of Chris McDowell's Into The Odd game - which is incredibly easy to convert into Heroes & Other World, by the way - and among it's many delights I was particularly taken by its rule for "critical damage".
In spirit, this reminded me of my own stab at making combat 'more bloody' back in 2013 (for Crypts & Things at the time) and inspired me to concoct the following houserule for HOW that I'm calling "Bloodied":
When a character (or monster) takes ST(rength) damage, he/she/it immediately makes a 3/ST save or collapses for 1d6 rounds, unable to do anything except crawl and defend herself* (NB. non-humanoid monsters will, instead, attempt to flee the battlefield to lick their wounds).Clearly this isn't going to affect heroes while they still have any EN(durance) left or enormous monsters with over 18 ST remaining, but it's also another way of changing the dynamics of battle so that two antagonists don't just stand toe-to-toe and keep whaling on each until one or other runs out of "hit points".
* Available Defensive Reactions: all out defense; block; parry. NB: attacker will receive the 'attacking from a higher position' bonus of +2 to hit & damage.
[TEXT REVISED/CLARIFIED - 4.50pm, March 29, after discussion on Facebook group]