Do any potions have negative effects, and can they be thrown or only drunk?
No throwing. About 35% potions have negative or mixed effects. Most negative effects are balanced out with a different positive in the same potion. For example, you can get Iron Flesh Potion that reduces your speed but makes you more resistant to hits. Or you can get Overdose Potion that fully heals you, but you get reversed controls for one battle. One of the potions I also plan is Barbarian Potion that increases Melee but reduces Magic. So, that one is great if you are a fighter, but if you play as a mage then it's negative.
Here are some other mysterious-potion effects.
Magic skill determines the damage and size of magic projectiles, and effectiveness of magic caused effects like using magic to buff weapons with poison. The game will also feature magic scrolls and the player would need to have a certain magic skill threshold to be able to understand what the scroll does before using it. Of course, if you are a warrior, you could still read the scroll and activate its magic, but some of the scrolls have really bad effects.
Potions can also increase your base skills, even to the point where it would make sense to switch class. For example, if you buffed up archery skill and range a lot, it would be a good strategy to start using bows and arrows.
Every game has some elements that are boring and unexcited to make but still important for player experience. Here are the boxes and barrels.
You can break barrels and boxes and find some items inside. Usually it's food and coins, but sometimes you may find keys, bombs, arrows, potions and other consumable items.
This was the first time I made animation of stuff breaking like this, so it was an interesting experience.