i rarely get hit from this boss, its "rain" will stack and keep on increasing. so just keep on running few square away every ONE hit you make. eg. enter room, hit, run, hit run, and cont... without any further delay. actually if solo, every boss is quite easy if you make some preparation like a few short fins. armor not actually important in solo, but in party then that is different case(boss stronger) beside Furnished boss, other boss i can just kill it without eating any food, except Luminescent Icefiend which i need to cook some short fin just incase, from what i saw i wasnt getting hit with the rain attacks though i ran out of them as soon as i saw them. he was triple hitting me most of the time doing 100+ damage each hit.