Personally, don't see the point of the beasts spawning in front of the villages, for a few reasons:
It'd hinder the players inside the villages the most, what with having to fight it every week just to pass through their gates and, say, go out to trade/interact with other villages? Plus, the enemy shinobi could just plan that beast INTO their strategy, allowing them to attack during the chaos and confusion of this (rather annoying) spawn.
The hero effect makes no sense, in my opinion. Sure, after the first time you might get something like that, but after the 30th time, this would just get annoying.
Overall, it's just better to have it be a random map spawn, not a village hindrance. If anything, these random spawns SHOULD BE the ONE type of time that rival villages need to team up to take such a monster down, otherwise it'll just roam around destroying everything. Even in WoW, I don't think they had those zone clearers spawn right at the player entry zones for each map.
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