i've seen a video of a Filipino blacksmith 'poisoning' a blade with dead venomous spider mash. he then heated the blade red hot and hardened/quenched and tempered it. i'm fairly sure no viable poison, if there ever was any, remained. purely symbolic/magical at that point.
as noted, the keris is treated with an strong arsenic mix to make the patterning stand out, but very little remains that could harm anyone more than being stabbed with it. do not drink the blackened water or lick the blade tho
