Godly Rage

you gain a rage meter, after you've unalived up to 4d20 enemies, you can enter a godly rage as a bonus action, this kind of rage isn't like a barbarians rage, this one is cranked to the maximum.

upsides: 

your skin becomes so thick that you only take 1 damage or nothing.

if you fail to get a critical hit, you instead deal a double critical hit.

whenever you deal damage, you heal equal to the damage taken.

you are immune to every condition and magical damage

you can restrain enemies as if they weigh nothing.

downsides: 

your speed is halved

you can't use any speed related actions

lasts for 5d10 seconds (up to 5 turns in combat)