A D12 System

The system relies heavily on using a d12 as the core random chance die.

That d12 roll will be adjusted by your modifier and likely coupled with a d4, d6, d8, or d10 

Unintentionally, the d20 will be your least used die.

A Player Driven System

The Game Master rolls no dice. If the player acts they might be called to roll against a challenge rating.
If something acts against a player character, the player rolls to react to that action's challenge rating. The players decisions and their rolls of the dice are the driving force of the stories.

Reliable Abilities

There is no such thing as "running out of spell slots".

Limited resources are attached to upcasting or exerting further effort.

However, there is a system called Weave Rot that risks punishing you for abusing magic in this system.