Saving Throw How To

Saving Throw is a Rune that lets you survive one killing blow and get a chance to recover health. I didn't experiment with it thoroughly, but it states killing blow, not death in general. So if you are about to die by falling/platforming, there is a high chance that Saving Throw won't save you at all, you will die.

Saving Throw does not hold major importance on any difficulty except Ultra-Nightmare, since regardless the other difficulty levels, you can restart from your latest checkpoint upon death, but on Ultra-Nightmare, it is one of the most important Runes besides Vacuum and Ammo Boost (in my opinion, others will argue for Rich Get Richer instead of Ammo Boost). This is because on Ultra-Nightmare, you have one life. You die, all your progress, your whole campaign is lost, and all you can do is start a new campaign from the beginning. Needless to say, getting one chance to survive a hit that would have killed you under regular circumstances is an advantage that you can't throw away on this difficulty. It can efficiently save your whole run.

To efficiently use Saving Throw, first you must earn it. It can be found near the end of Lazarus Labs, at the small fight following the Lazarus wave activation replay, before the final big battle of the level. By final big battle, I mean that big area with lots of enemies in it, not the Cyberdemon boss fight. See video for details.

Once you have earned the Rune, you can equip and use it. While most Runes don't affect the appearance of your HUD, Saving Throw shows its status in your HUD also. Once equipped, a hourglass symbol appears at the right side of your health and armor bar, signalling that you have the protection of Saving Throw. See video below.

This should technically be 2 topics, but the video in this section shows how both look like in-game.

Once you have Saving Throw equipped, it lets you survive one killing blow. I must emphasize again that it doesn't save you from deaths by falling/platforming, but you can survive a hit that would have killed you under normal circumstances, be it from enemy or yourself. If you are a Rocket Launcher fan like myself, or failed to notice an Explosive Barrel and don't have Explosive Barrel immunity (unforgivable beyond level 7 on Ultra-Nightmare, but who knows, there are masochistic players), you know what I'm talking about.

It is important that you keep in mind that when Saving Throw acts, your health doesn't regenerate to 100 (or any comfortable level), you will have a measly 5 hp and some 2 secs in slow-motion to figure out what the hell you should do to restore your health. If you are not in a boss fight, pull BFG, shoot and swim in health.
If you are unlucky enough to be in a boss fight, pull BFG, pray that it hits the boss in the right manner to stun it, then shoot with other weapons and maybe you will get some health. Except Hell Guards, because Hell Guards are stunned by shooting them at the right moment when they charge their energy shot, you have to figure it out on your own. BFG works on them also, but timing is critical. I prefer to shoot them with Chaingun Mobile Turret, that way I surely catch the right point of time.

The amount of time the slow-motion covers is less then a second in "real-time", but at least you have the advantage of making decisions while the environment slows down for a short while. Once Saving Throw has acted, the hourglass symbol disappears from your HUD, signalling that you are susceptible to death blows for the rest of the current level. However, if you are lucky/tactical enough, there is a huge perk, which is

Any enemy that you kill during slow-motion adds a number to progress towards the upgrading of the Rune. You will have to get a total of 10 kills during slow-mo to get the Rune upgraded. Upgrading the Rune lets you survive another killing blow. Add in that it resets on each level, and you have basically 3 lives per level for the rest of your campaign. On my first accomplished UN run, I should have died at least 4 times, but Saving Throw II pulled me out, twice alone on level 12, Vega Central Processing!

The optimal scene to gain the upgrade once and for all is in Titan's Realm, after the second big battle, the one with the Quad Damage and the 2 Barons appearing at the end of it, when you arrive at a room with some Lost Souls and many Hell Razers and Unwilling waiting for you. Best way to earn the upgrade is:

After you have finished the main battle, switch your Rocket Launcher from Remote Detonation to Lock-on Burst. Believe me, I have blew myself up once with absolutely nopony nobody attacking because I was dumb enough to try to bring my health to threshold with a mastered Remote Det rocket BEFORE I equipped Saving Throw. So first, switch to Lock-on Burst.

Then equip Saving Throw, DON'T FIRE ROCKETS IN ORDER TO BRING LOW YOUR HEALTH BEFORE EQUIPPING THE RUNE! If you have Saving Throw equipped, and mess up and blow yourself up early, you still only fail the upgrade, but can continue your run. If you blow yourself up before activating Saving Throw, your torment will be ended.

Now you have Saving Throw equipped, and you stand before the arena with the soon-to-be dead Lost Souls and other monsters in it. Good. Shoot a BFG, then kill yourself with rocket as soon as possible while running into the arena. If you don't run into the arena, most of the grounded monsters won't spawn and that measly 4 Lost Souls won't be enough to cover the 10 kills you need to upgrade. See video below. Watch closely that the hourglass symbol disappears the moment I get a killing blow by myself, then reappears after upgrading the Rune, signalling that I have another chance to survive a death blow.

Which I didn't know that I would need so soon, but I did, as seen on the second video.

If you have used up your chance at Saving Throw (once in the case of earned, but not upgraded, once or twice in the case of upgraded), it will reset on the next mission/ level only if you had it equipped while completing the actual level. If you didn't have it equipped at the moment you finished a level and you have used up your chance(s) on the current level, equipping it at next level won't reset it and won't give you the chance(s) to survive death blow(s). Watch me equipping it before the final battle in Titan's Realm. Since I have used up both of my chances, the hourglass symbol doesn't appear even though if I have the Rune equipped. However, after I finish Titan's Realm, and progress to The Necropolis, the hourglass symbol reappears, showing that I have the protection of Saving Throw again. Failing to equip the Rune before finishing the level is NOT recommended. You will need that Saving Throw during the Hell Guards boss fight. Unless you are a Jedi. Good luck, warrior. But your journey has only just begun.