Sun is a new legend from recent update and as a new in the league, I believe that there are lots of players asking for Sun build and strategy guide. Just like the Sun or Monkey King from other MOBA, he is based on deception and tricking his opponent for his advantage. His passive is about summoning a doppelganger that gives him HP regen based on his attack. His first ability is the Golden Cudgel Strike that deals 120 physical damage and slows the movement speed to 40% for 2 seconds. And for his ultimate he is going to summon 2 clones which double the overall arsenal of Monkey King. To make your Sun effective in battle here is the list of items that must be present in your every match:
Item Build
Just like with Chou’s build you will start with Crazed Reaper that gives +65 physical damage, 20% attack speed and +300 HP. This item gives everything you need in laning which are damage, attackspeed and HP for sustain and defense. To boost your sustain with your passive even more your next build should be Tooth of Greed that boost you with +75 physical attack and 25% lifesteal. That will gives you lane dominance especially after you reach level 6 for ultimate. And lastly for your core items, just add Tough boots that gives +40 movement speed and 22 magic resistance. I like building any melee based legend with armor/magic resist so it will stands in team fight longer. There is no point to focus on full damage unless you are carry. But considering Sun, he has the kit with almost all damage and what you need to improve is to make him stay longer in team fight or enemy team can easily zone you out or kill you.
For additional tankiness, you can buy Cursed Helmet for additional 920 HP and 50 magic resistance or Bruteforce Breastplace for HP and armor. Just build an item based on what type of damage does your opponent doing well. If you see that they are focus on spell caster, you can go for magic resist otherwise just always go for armor.