Vergiftungen mit Tränken geht leider gar nicht
Poisoning with potions is unfortunately not possible
I did some testing...
Clicked the Poisoning Skill > Targeted a Food Item > Targeted the Poison in a bottle.
I ate the food (a cake) and I got poisoned.
Clicked the Poisoning Skill > Targeted a Dagger > Targeted the Poison in a bottle.
Attacked a Dog and it got poisoned after 2 hits.
Poison skill gain did go up while I was testing as well. Give it a test and report back.
