Sold on Saint Patrick's Day exclusively, similar to the Patriot's Flag.
To keep it from being a reskin, it has the effect of repulsion (see Phial of Galadriel) as opposed to healing.
This makes sense to me personally, seeing as Saint Patrick is credited with ridding Ireland of the snakes which is usually interpreted as him repelling the unholy from Ireland.
EDIT
Coming back to this to list some reasons I suggested this;
St. Patrick's day is soon - 14th of March
Uses;
-To set up a permiter after defibbing someone
-To prevent camping on objectives by brutes & skullguard champs
-When swarmed or needing to use medkits
Cons;
-Takes up a secondary slot
-Hard to hit with, awful stats as a melee
-Essentially the patriot flag with only a mesh, audio and effect difference