Critical Attacks
Any roll of natural 20 on a 20 sided dice during an attack is an automatic hit. Roll the D20 again and if the roll result is equal to or greater than the armor class of the target then the critical hit is confirmed and rolled damage is doubled.
Emphasis Roll
For use on any roll that only has 2 outcomes, very well or very badly. Roll a D20, results above 10 are good and below 10 are bad. The number furthest from 10 in either direction will be the final result.
Feats
Any and all feats from D&D 3.5 can and will be converted to 5e with the same level progression from 3.5.