In the Ransei period of Kitakami's history, tea was high culture, practiced by warlords and intellectuals alike. Tea masters were as prestigious as elite pokemon trainers, and the ceremony around tea, unlike its highly simplified modern counterpart, was an elaborate and competitive ritual which could take a lifetime to master – or longer.
Entropy has doomed many a tea bowl or other beloved heirloom, and Poltchageist seek to preserve their equipment – down to the house they lived in, or at least the room where they served tea to guests – exactly as it was in life. In all fairness to these pokemon, however, it is not as though they could exactly go out and purchase replacements. Poltchageist can make a powerful solvent out of matcha, which repairs cracks and holds items together, but its sharp green color often clashes visually with the rest of whatever they have repaired.
It is not only cracked objects which Poltchageist seeks to seal, but the flow of time itself. Foreign trade had begun to undermine Kitakami's traditional culture, so Poltchageist, with the support of the domain's warlord at the time, used its green matcha to seal cracks in the territory's notoriously strict and fortified border. But without access to the outside world, this pokemon could not know that tea had become as popular a delicacy abroad as it had in its homeland; when the invaders and their Lickitung slurped up the tea and Mossui Castle crumbled, nothing could possibly preserve Kitakami's isolationist policy.
Many barbarians were cursed on that day, but many others received a tea ceremony for the ages.