A simple mod that adds 2 items that you can use to become an immortal, before it runs out, where you become weak and frail.
Find philosopher's pebbles as an or in the nether, and combine 5 of them into a philosopher's stone along with a quartz and a gold nugget.
in a pinch, use it and you'll gain immortality for 10 seconds, where you will only be killable if you take 20 damage, however when the effect ends, you get down to 3 and 1/2 hearts.
Video of philosopher's stone in action
(I plan to change the effect to be your last half heart is immortal, I think that would be more balanced
