Most of this game may be skill and speed, but it does require a serious amount of luck to manage a good speedrun.

Relics that are the most helpful to finish quickly are the following:

Damiens Amulet: It greatly increases your damage at the cost of mana. Holy Bible/ Amputation Kit: Saves you time with cliffs and at the same time protects you from floor traps. Holy Water: Protects you from all damage for a short while. Ankh: Gives you one extra life. Good during the Damien Head boss round and on encounters with Kayo the Sapling.

Relics that are not great but are useful: Staff of Apocalypse/Rocket Barrage: Multiple explosions that can instakill enemies. Saves time when filling the boss meter. Butcher's Knife: Passive chance of a shockwave that travels a long distance and deals a lot of damage. Sword/Cube/Armor/Dagger/Bracelet/Axe : Stat friendly Relics Templar's Shield and/or Guardian Angel: Blocks projectiles, shoves enemies back. The Glove: Saves time when picking up potions and relics.

Things to watch out:

1. Always look at the boss meter above. Once you have killed enough enemies, go to the encounter.
2. Do not waste time with puzzles, dungeons, crypts and areas with traps. Get relics from bosses. There is a high chance they could also drop from diamond chests. If you see an area with corridors of traps or puzzle areas and there is a crucial speedrunning Relic in them, attempt it at your own risk. BUT! When you open chests step away before they open. If they drop the King's Crown and you pick it up, you must restart the run from the beginning, as the King's Crown is forbidden (Unless you have the game updated to 2.0.0.7 or newer patch).
3. HOPE that you do not encounter Kayo the Sapling in general. He has skulls spinning around him that deal enviromental damage. Meaning they deal the same damage as a regular spike trap.
4. On ACT 2, AVOID the snow goblin boomerangs and the shards that come out of them when they erupt. One hit and you will be stunned for 3 seconds.
5. The Grim Reaper battle cannot be finished instantly, because you have to avoid the skulls. Stand near the blue skulls and when they disappear, move out of the circle. Continue like that until the sythe pops up. Hit the sythe and stand on the pentagram, cause when it hits the Grim Reaper, the gate pops up and you can move on. Also, when trying to avoid the skulls, stand near the blue skulls and WAIT for them to disappear. If you come in contact with them, you die.
6. Damien in the first encounter is somewhat easy. Unfortunately for you, the Damien Head round is nerve rackingly difficult. You will spawn in an area with four squares, three of which will disappear. If you are standing on one of them without any flight, you will die. If you are inside the squares, while they explode, you will die. The one square that remains is the one with the pentagram.

Have fun :)