Timer starts once the loading throbber on the bottom right dissapears.

To begin, you will need upgrades. Specifically, Wraith class (shard upgrade), Shotgun (double barrel preferably) and black katana (other good weapons might come in handy if you can't find a black katana). Upgraded starting weapon will be very useful to you (Good chance for DB shotgun/black katana, saving you time). Ammo upgrades for ranged weapons really help in the finale, the more shots you get with your OP DB shotgun, the better. Any other upgrades will help too.

You will also need to have unlocked Islands (I believe you need to defeat the Necromancer, I am unsure however) and the shortcut to Crystal Caverns (absolutely required).

As for the route, its Caves I (Pick up the starting weapon, perks, and map piece), Crystal Caverns I (Find the altar. Often enough it is in the first room, maybe a few rooms away however. If you cannot find it within a reasonable amount of time, restart. What amount of time is reasonable is up to you), Islands I (Best place to look for shotgun/katana if you do not have them yet, but otherwise simply hunt down the marked enemies, often enough they are shard lords, and leave), Islands II (ignore absolutely everyone and charge to the Aberration, all other enemies will immediately despawn, and kill him. The fight is relatively easy: blue tentacles shoot fireballs that will never hit you unless you stand still, and red ones hit you, but need you to stand near them to do so. Try to hit any rising tentacles ASAP as they will retreat into the ground again after a few seconds), Blood and fire (be careful as enemies can spawn inside of you, watch out for pursuers, also you need to clear each island before being able to continue) and finally the end.

Fighting the End is relatively simple, as long as you remain mobile, he will never hit you. The skeletons are quite literally zombies reskinned, and they bring weapons in case your katana breaks (never happened to me however). The end has a few attack types. First of all, airstrike (he will kneel and look up i believe), causing bombs to rain down. Easy to avoid as each bomb's landing spot is marked. Secondly, the ground laser explodey thing, where he kicks the ground and sends damage and pain towards you. Easy as all hell to avoid (I see a theme developing). Third, his area of effect self bomb. He will kneel down and deal damage around himself. Surprisingly, its easy to avoid. However, he himself is invincible, until you defeat his minions. At set intervals (I believe, might be tied to how many skelebros you kill) they show up, in pairs. This is where the shotgun finally comes to play. Starting off, Centurion and Pyro (easiest 2 to kill: Pyro has low HP: one shotgun blast can kill him and Centurion is slow as all hell, although his shield prevents easy shotgun kill). Once they die, their respective pillars lower. Secondly, Crawler and Beast (crawler is tricky, best just cut a leg off in between his attacks. Beast is breakfast for your shotgun as long as you hit head shots), and finally Golem and Deceiver (Kill the Deceiver first before they can even execute any of their moves, 2 shotgun blasts or a few slashes will do. Golem, like the Centurion, has HP but not speed. Shotgun headshots, and backstabs will do). Once all shard lords are down, the End turns into a normal looking guy, and finally becomes vulnerable to your attacks. Just get behind him and keep slashing at him: he has quite low HP.

Timer ends once the End dies.