Basically, everything pertaining to how any entity in the game acts towards any other entity is governed by the faction/reputation system. The wardens (of Joppa, Kyakukya and any other village) are their own faction. Same is true for the dromad merchants and the zealots. You probably managed to kill a legendary who was loved by the Fellowship of the Wardens, which made him hostile.

Managing faction reputation can have a big impact on your run. There are some factions where neutral/positive is extremely desirable, like robots for example, as it makes some really scary stuff not obliterate you on sight. Always look at legendaries before fighting them, and if they are loved/admired by factions you don't want to be hostile with, avoid them. You do not need to fight everything in Qud.

Same is true for the water ritual. If someone friendly to you is hated by someone you don't want to get in trouble with, don't do it.