You can stick to surfaces, allowing you to climb any solid surface, including sheer walls and ceilings without issue.
Climbing using this ability requires neither of your hands.

Normally, every 5 ft. you climb costs an extra 5 ft. of movement. With this ability, climbing does not cost extra movement.
Normally, climbing requires the use of at least one of your hands, which may be empty or wielding an object useful for climbing. With this ability, you can climb with no hands.
Normally, if you try to attack while climbing, you suffer disadvantage on your roll to hit. With this ability, attacking while climbing does not impose disadvantage on your roll to hit.

You also deal extra poison damage with weapons and spells which deal damage.
(This damage boost does not affect buff spells which make something do additional damage.)

You can end this spell as a fast action.

Subtle:
Casting this spell while hidden also hides that you are casting it, and does not cause you to become unhidden.
When you cast this spell while you are not hidden, you can try to hide that you are casting it with a contest of Spellcraft or Roguery against the Seeking of creatures observing you. Only observers that win notice you are casting a spell. However, once the spell is cast, its effects may be noticed.