Teleportation

When using the spell Teleport, if the caster does not have a clear view of their destination (either line of sight, or via scrying or the like), there is a chance they will arrive high or low of their intended spot. This does not apply to natural abilities such as what demons have. It does apply to Teleport Without Error when teleporting across planes, and does apply to the Helm of Teleportation, per the DMG entry.