If you use an item or spell that turns you invisible you cannot wear your mounts or a specific outfit as you turn into a blob of sparkles for lack of better terms. Mounts give you a +10 speed boost so this can be quite annoying if your a lower level. Also, if you're trying to turn yourself into a creature by using the utevo res ina spell or if you use a Chameleon rune it will cancel out the invisibility if you're using the utana vid spell or if you are wearing a Stealth ring it won't work. You won't be able to become invisible if you're swimming, as this changes your appearance as well. You won't be able to use costume bags, they won't disappear if tried but a message will say "You can't use this bag while you're invisible."