Dice, action economy, actions, attributes, and proficiency. We have skills, but they're mostly your standard stuff. Nothing crazy like some games. A few have actions tied to them that were mentioned with the actions post. Magic. It's a fantasy 2d10 ttrpg, so there's magic.
As a proud hater of spell slots we're going mana points. 9 always felt like a weird number to top out at, so we'll do 10. A spell costs an amount of mana equal to its level. Easy. How powerful a spell is should be directly tied to its availability.
8d6 is too many for a 3rd level spell. 6d6 too. We'll match the d6s to the spell level, so a 3rd level spell will do 3d6 aoe. That doesn't blow the martials out of the water and still gives the caster a lot of power. How does magic work here? I'm going with Wheel of Time.
Strands of elements to be woven together; no material components. The elements need to be distinct without being complicated. Air Earth Water Fire Lightning Light Time Spirit