On Top of Praetor Suit tokens and Weapon Upgrade points in Doom Eternal, you also have Sentinel Crystals. Sentinel Crystals are used to upgrade the amount of Health, Armor and Ammunition that you can have. They can also provide extra boosts when applied in certain ways.
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Using Sentinel Crystals
You can find Sentinel Crystals through the levels in the game and they are marked on your map, once you find the automap. So you should start to unlock them passively, without putting in too much effort to find them (hopefully).
Once you find the Crystals, you will be taken to a screen where you can select the upgrade you want, split between the aforementioned three options. If you select armor or health, those stats will both increase by 25. If instead you select ammo, it will increase the cap for all types.
You can also receive an upgrade if you select two options from both sides of a cell.