When used, it will set the stats of a monster of your choice to 3/2.
Using this makes a monster able to avoid cards like Muffet's Pet as well as Asgore, but makes it fairly weak. However, you can combine it with Asriel or (when absolutely needed) Heal Delivery in order to bring their HP back to its original.
You can also use this on enemy monsters. By bringing it to 2 HP, you can instantly kill it with the help of Temmie, Ice Cap or Papyrus. And Papyrus will even not take as much damage due to the monster's ATK also being lowered to 3. Useful in disabling a Mettaton NEO, as it will bring down its attack and also make it more difficult for the enemy to trigger its dust effect.