The potion of see invisible enables you to see invisible monsters. Blessed potions give you the intrinsic permanently; uncursed and cursed give you the intrinsic for a number of turns. If it is not cursed, this potion will also remove blindness.
When drinking this potion, you receive the message "This tastes like [fruit; default is slime mold] juice." Similarly, the cursed version will taste "rotten." The potion of fruit juice has the same messages; these are therefore difficult to tell apart by random quaffing. They also share the same base cost. Some ways to tell the two apart include:
- If you were blind and were unblinded, it was see invisible.
- If you see previously invisible objects/enemies after quaffing, it was see invisible.
- If you were invisible, you get the terribly worded message "You can see through yourself, but you are visible!"
- Put on a ring of invisibility and if you get the message "Gee! All of a sudden, you can see right through yourself." rather than the normal "Gee! All of a sudden, you can't see yourself." then it was a potion of see invisible.
- Zap a wand of enlightenment or otherwise attain enlightenment. If you have the see invisible intrinsic, it was see invisible.
- Fruit juice is sold in a delicatessen; see invisible is not. If you see one of the two in a deli, it's fruit juice (or booze). Likewise, if a deli buys the potion, it's fruit juice. A delicatessen shopkeeper will not buy see invisible.
- Dipping a unicorn horn into a potion of sickness turns it into fruit juice.
- Dipping an amethyst into a potion of booze turns it into fruit juice.
- Cancelling a potion of sickness or see invisible turns it into fruit juice.
- If you are on the border of a hunger change and it disappears upon quaffing, it was fruit juice; however, this is difficult to test.