the reason for the items is you start with boots to get your movement up and you have the 2 hp potions and a mp potion for harassment also pantheon doesn't have all of his defense at a start of a fight so you have to plan for taking a bit of damage then moving into the brutalizer for some damage and cool down then modify the boots of speed into Ionian boots for more cool down to have then the blood thirstier to keep your life steal up and to deal more damage moving into the Atma's impaler for some armor and critical chance also pick up some more Attack Damage the warmog is used to for life regeneration and a extra 1k health for long fights and being a part tank champ also the Atmas impaler will give you some extra damage from the warmog so it is also more Attack Damage then moving into the last blood thirstier to kick the life steal up more and your damage when fully stacked both bloods give you a combined total of 50% life steal and that brutalizer will be finalized into a youmuu's Ghostblade

spear shot is good for harassment at start of a game you can easily hit squishy champs and even break apart their armor, it also is used for a kill shot on a champion after you do your sequence of skills

Aegis of Zeonia is used to hold the enemy in place while you beat on him with your heart seeker also if for some reason you get stunned while using Aegis the good thing about it is it will protect you from the next hit for it already has your shield ready.

Heartseeker Strike makes a small cone of damage that rapidly hits the enemy(s) in your path the use of this skill would be to combo with aegis so then the target has no choice but to take the damage you lay in front of him/her Also as a passive bonus when you hit anything at 15% or less hp you have a 100% guarantee for critical strikes

Grand Skyfall is the ultimate that makes or breaks a fight (literally) with a range of 5500 units pantheon can jump to almost 1/5 of the map and this will allow him to do 2 things either hit a huge cluster of enemy champions to start a fight or to get to one place in a few seconds. they way the skill works is you select a targeted area for him to jump into the middle of once selected it has a 5 second jump time then a 3 second land time so you must prepare for the any movement of the targets to go anywhere before using it.