Before I get into the bread and butter of this guide, I would like to acknowledge the players who designed/created this build. Many thanks to Ankan V2, Ankan, and Senfgas for designing, playtesting, and building this build.

Phsyco Singed has an 80% winrate in diamond 1 EUW at the time of writing this guide.
(22/08/2019)

Phsyco Singed is a variation of roaming Singed which is oriented around the use (And abuse) of the Predator keystone paired with movespeed active items.

Always start Boots of Speed and Refillable, Dark Seal start has been tested and it doesn't provide the oomph that starting Boots of Speed does, having Boots of Speed you are able to use the Predator passive to get back to lane extremely quickly from early recalls. A similar technique was used by Minishcap1 for a period of time so that he could play aggressive in the first 5-6 waves and then recall to refresh his health, mana, and potions and he wouldn't lose out on much XP or gold as he'd use predator to run back to lane quickly enough to catch the wave as it crashed into tower.

Always first item Boots of Swiftness (Even if you're getting abused in lane) and keep your eye on the map for any potential skirmishes you could Predator into. You MUST give up a lot of lane presence to roam for these skirmishes but don't be demoralised if you start falling behind, so long as you can keep the map pressure up you will outscale your laner.

Once you are in the mid game (About 15 minutes in) you should be well on your way to building Shurelya's Reverie, 99% of the time you want to get Aether Wisp first, but in certain cases where you are getting destroyed regardless of where you roam to, get Kindlegem. Lane ganking once you shove your lane is the key to winning the mid game, hard shove your top wave and then recall, look to run mid or bot with Predator and ghost (And Shurelya's once you've built it) to surprise the enemy with a 550 movespeed Singed coming in to fling. In most cases this will result in them blowing summoners, but if you use your W strategically (Throwing it to prevent movement abilities at the right time) you can often get kills. Use the pressure you've put on mid/bot to secure dragons and then reset to go shove top lane in.

There isn't much to add here, especially seeing as the Singed players who I have been analysing using this build don't often go to late game. For the most part they produce too much pressure for the enemy team to counteract and win the game within 25 minutes. The "Build Finishers" are mainly speculation as for the most part these players never get that far into their build. To close out the games in the later stages of the game, ZZ'Rot is great. Put the ZZ'Rot in a side lane and keep an eye on it, try to shove another lane with your team and if anyone goes for ZZ'Rot you should be able to catch up to them in time to prevent its destruction (Considering you will have very high movespeed) this helps pick off enemy players and divert pressure which lets your team push further into the enemy base.