This is a build for Thanatos I've been strongly advised against and not found online, but it works well for me. Since I don't find anyone else doing it I figure I share it. This is intended for Arena. Also auto build because I'm a noob and ain't nobody got time for manual stuff. Also doesn't really work too well if there's a loki, he is consistent instant death if targeted.
This build is very squishy and doesn't have much power either. It capitalizes on Thanatos' abilities' guaranteed damage/effects, having just enough power to do some base damage over time, and most important of all, having teammates to do the majority of the damage to your victims. This may sound like it's a useless kill stealing build, but it's geared towards helping by catching as many gods as possible as they run back to base, thus, minimizing the wasted damage/efforts lost to enemies being able to retreat and heal in base. It's a very squishy build and requires you to be very alert/active to be both effective and evasive.
Your main goal in mind is catching all the low health gods and not letting them back to base. With this full build, you can run out of base, hit your Scent of Death ability while there's an enemy in the kill threshold 3/4 of the way across the map, zoom across the map (attracting the attention of most of the enemy team usually) and slice them up as they're running back. Using your other two skills you shouldn't have much issue getting the kill. Bloodforge will give you protections, power, and a speed boost to evade the horde of enemies that wanna catch you. Fail to get the kill, and the right god with the right build can manage to get you sometimes, keep an eye on the minimap. Your ultimate becomes a secondary tool for getting kills on low health gods, in fact I find it more useful for attacking gods at full health, tossing everything else at them immidiately, while dipping outta there and waiting for the teammates to chip them down a bit more.
While no gods are damaged, you can use hit and run strategies to passively contribute. Soul reap is good for killing protected groups of minions on the go, bonus is if you hit and silence the gods that are by the minions at the same time, then just before they know you were even there you're already gone. Swoop in on a teammate under attack and soul reap their attackers to silence them, then get out because you're fragile. You aren't useless you still have combos, but you aren't really going to put out much damage. Also, if your team is not the greatest and is being annihilated and killed right out of the gate as wave after wave of minions goes through your portal, it's a good build to break out of that bad position, zoom across the map, and just go start killing the minions at the source, break the stream, and/or draw them away from your base so everyone isn't funneled into such a small target.
I favor the attack speed buff, as it works well for attacking a lot of unguarded minions, as you can just circle around a big group and have at it. Plus it fits the speed theme. Also contributes when chasing down low health enemies. Grab it when you see it.
In general, if the enemy has a long ways to run, your base attacks should be good. If they are almost there, or are fighting back, use your abilities. Use your own discretion, don't forget to get a jungle buff before you need it.
Talaria Boots meant for the large initial speed boost, especially paired with the equally large 7 second boost every time you leave the fountain (very useful).
Bumba's Mask is chosen for the massive speed boost, and placed 2nd to put you above everyone else's speed right away. Careful though, you're fast but still relatively catchable with abilities. Other gods (assasins) may still have high speeds similar to yours at this point.
Hastened Katana is 3rd because you now have a core high speed as well as the 20% boost each time you leave the fountain, plus Scent of Death ability. This is enough to start chasing them down, and hastened katana both adds to your base speed, as well as allows you to hack and slash on the go without slowing down.
Winged Blade is for immunity to slows, with the added bonus of the slows being converted into an additional 20% speed boost. There's also crowd control reduction and much needed health for those occasional screw ups or more audacious maneuvers. It's not much, but you find yourself barely alive pretty often. Makes a difference. With your movement speed, barely alive is as good as alive. You have healing poitions, lifesteal, are highly evasive, and a trip to the fountain/base is always quicker than teleporting.
Masamune, I really don't know why I think it's just the best option I can find. It's a speed boost. I use the sephiroth skin so it kinda is meant to be. The passive is nice though for when swooping in and out of large groups of enemies, or being chased by the entire team and those few ranged attacks manage to hit you before your Scent of Death cools down.
Bloodforge is there to help get that last hit in right as they make it into their base, the extra umph you need, more importantly, the perks that come with a successful kill. Protection and more movement speed, which helps with the angry mob that's usually right behind you. Makes evasive maneuvers easier.
Purification Beads, nuff said. People will catch you occasionally.
Phantom Veil. I don't really see any other relic being useful. Aegis, I feel it's not really a high speed relic. More of an oh no im a turtle, time to go in my shell sorta relic. Phantom veil just kinda fits the theme of untouchable inescapable yet frail phantom. Pass straight through the occasional ymir wall or body blockers. Or save a teammate if quick enough on the draw. More of a relic for keeping with the theme, psychological warfare part of it.
Chalice of Healing, you'll use this a lot.
Chalice of the Oracle, Idk, I just like my wacky inflatable waving arm ward. Place them all over the place. I'd get a consumable for power or something but that's too much for me right now, i start using too many abilities and i hit the wrong button, then get all sorts of mixed up and before you know it there's 50 different menus popped up on my screen and im dying while trying frantically to figure out how to close the menus and reposition my fingers on the right keys lol.