Get a mustardy right at the start by combining zuum with suezo.
Make sure it is at least B grade after 2 and 1/2 years. A traveller will come and ask to use your monster in an exploration say yes and go streight to the mountain where a pheonix will burst out. explore the mountain until u find a fire feather and then go back to camp. your mustardy will have to be retired then so go to town and combine it with another monster and use the fire feather as a secret seasoning. It will come out as 100% pheonix which never dies.
Added by: It doesnt matter.. , ID#5684