Our mudlib supports the ability to poison players.
To poison a player, the following call in the player is used:
    this_player()->add_poisoning(amount);
where amount is any amount.

A poisoned player loses hp, rather than regenerates hp.  The amount the
player loses each heart beat depends upon the amount of poison.
Strong poisoning is 40.
Also, cleric purification spells and the hospital purify in amounts, so
the more poisoned, the more purification spells need casting.
	-Descartes