If you have poison resistance, you're good to go while poisoned. There I said it
BUT
What you did was come into melee range of an SMC creature that was probably a unique monster too (purple, you mentioned) and likely had more deadly than average poison attack.
For what it's worth, a char of your caliber with single source of poison resistance would need a quickling queen to land several poisoning hits to accumulate enough poison for it to become a threat and kill you this quickly.
Again, you went through SMC which defies even the tiny few shreds of logic that ADOM possesses, once in SMC - forget all you have learned and expect kobolds damaging your eternium plate mails and worms giving you more poison than quickling queens.
"Hell is empty and all the devils are here."