Eikythr is the first boss you'll summon and can be quite challenge if unprepared. You'll want to make sure you have a full belly of cooked deer, neck, and boar meat. In hunting deer and boar, make sure to grab the deer hide and scraps in order to make a full set of leather armor. Eikythr primarily does charge attacks and AOE damage, so the best coarse of action is to stay far away and pelt him with arrows. Flint arrows do the most damage, but wood arrows are the cheapest to make and you will need a large amount of arrows to take the deer god down.