A cooked heim crab can either be found on the table at the start or by killing monsters in the dungeon and receiving it as a drop. A raw heim crab can be bought from the Smuggler.
Other crabs in Daemonheim include the members only tier 9 blue crab, healing 1600 Life Points and the tier 6 web snipper, which heals 1000 life points.
While progressing through a dungeon and if hurt, it is best to consume the heim crabs first as they take up valuable inventory space but only heal 200 life points. This allows other, higher-healing fish to be put into the inventory. Many high level players do not take these off the starting table because they consider the 200 life points it heals too insignificant to bother picking up (it heals about 2% of the life points of a player that has 99 Constitution). Alternatively, they can be sold to the Smuggler for 72 coins, but are of very little use in a boss fight. The Jagex mods like to make jokes about heim crabs just like they do with cabbages.
If you try to use a heim crab on another player when their life points reach 0 you will receive the message, "Even the mighty Heim Crab won't save (insert player name) from their fate!". Also you will get the title "Too little, too late"
In Postbag from the Hedge, it says that if you hold a heim crab up to your ear, you can hear the sea.
In Behind the Scenes - December, Jagex quoted "Heim crabs are for life, not just for Christmas."
The word "heim" most likely comes from the word "DaemonHEIM". As Daemonheim means "demon home", "heim crab" may translate into "home crab".
If you try to use a heim crab on another player when their life points are full, it says, "As tasty as Heim Crabs are, [Player's name] has full life points".