Is it only creature-related?

The intoxicate ability doesn't seem to do much in combat but if you can hit your opponent's creatures with it, it should reduce your opponents stats temporarily once the fight is over. This can be confirmed by the trigger "intoxicated_by_[your player ID]".

The intoxicate ability is an interesting ability as it affects players after the combat, not during it. The poison of the plant-type creature known as the Toxicodendrite weakens the player hit with it and reduces certain stats for a limited amount of time. Better yet (or worse?) if you are hit by multiple players who have a beef with you (and rituals with toxicodendrite), you will find you need a cane.

The feeblesness needle is an item that can weaken you just as the poison from toxicodendrite does and once again effects are cumulative. The lesson to learn from this ability is that if people are willing to level up a creature only for this ability, you've really pissed them off. So to answer the question, it works to make you realize what a bad guy you are.*

^{*MD is a place for villains as well}