KNOWN ERROR:  Requires you to start 1 match after updating before the bar will start to fill in that match. It should then work in the lobby going forward even after a restart. No idea why.

This will display a number above the ult as you build up your ult as silver. There are versions with a displayed bar 

Green means you will ult if your hit goes under 30% health right now

Red means you currently are under 30% health and thus getting the multiplier to your build up (This is factored in)

The options are:

Damage remaining to ult (Moon Phase)
100 down to 0 (Moon Phase Countdown)
0 up to 100 (Moon Phase Buildup)

And a non-bar version of each that are archived to avoid confusion 

(Note: Countdown's bar will start full and empty as you damage to build your ult)

Conflicts with mods that use: panorama/layout/ hud_ability_icon .vxml_c 
Most should not use this as most mods will interact with one higher in the tree.

Forum post asking for a base game version:
https://forums.playdeadlock.com/threads/silver-ult-indicator-idea-posted-last-one-in-items-by-mistake.116762/