Amphibious.  The watcher can breathe air and water.

Tainted Water.  Any small body of water inhabited by a watcher becomes tainted within 1d6 days of the watcher’s appearance.  A creature that drinks from the tainted water must make a DC 14 Constitution saving throw. On a failure the creature takes 1d8 poison damage and is poisoned for 24 hours.  The watcher is aware of the location of any creature poisoned in this way for the duration, as long as they are on the same plane of existence as the watcher. Tainted water can only be purified by magic, such as through the use of a purify food and drink spell, but returns to normal within 1d6 days if the watcher tainting it is destroyed or removed.

Bite. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 4 (1d6 + 1) piercing damage.

Eye Rays. The watcher shoots up to two of the following magical eye rays at one or two creatures it can see within 60 feet of it. It can use each ray only once on a turn.

• Cursing Ray. The target must succeed on a DC 13 Wisdom saving throw, or become cursed for one hour.  While cursed in this way, the creature can no longer breathe air, and can only breathe while in water.
• Paralyzing Ray. The target must succeed on a DC 13 Constitution saving throw or be paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
• Silencing Ray. The target must succeed on a DC 13 Charisma saving throw or be silenced for one minute.  While silenced a creature cannot speak or use their body to create noise, and cannot cast spells that require verbal components.  The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
• Elemental Ray. The target must make a DC 13 Dexterity saving throw, taking 11 (2d10) points of either acid, cold, or lightning damage on a failure, and half as much on a success.  The watcher decides which type of damage the ray will deal each time it fires it.  The watcher may fire this ray twice in one round as long as each ray deals a different type of damage.

Create Food and Water. The watcher magically creates enough food and water to sustain itself for 24 hours.

Spell Reflection. If the watcher makes a successful saving throw against a spell, or a spell attack misses it, the watcher can choose another creature (including the spellcaster) it can see within 30 feet of it. The spell targets the chosen creature instead of the watcher . If the spell forced a saving throw, the chosen creature makes its own save. If the spell was an attack, the attack roll is rerolled against the chosen creature.