Creature can be obtain once after the 1st dragon transformation you experienced in broken valley. There is a necromancer in the broken valley which ask you to track down his creatures. After completing the quest, you should be rewarded an item call crystal skull, which you can use it to summon your creature. Drag the item to your hotkey for easy access.
As for your alchemist glitch, I think its better for you to send a copy of your save game to larian support. State your problem and ask for a fix on the save game.
