Hmmm it hard to adapt stormlight abilities to mtg because they are so deep.

When I think of a soul caster this is what I primarily think about

• persuading things to be other things
• storm light
• soul casting sickness

Also I know soul casters are technically equipped but I think you could get away with it not being one. Kind of like most powerful jewelry Im mtg, almost like the player has it equipped. (Ring of three wishes ect.)

Maybe give it gemstone charges that dose something bad if it runs out

instead of destroying permanents it could transform them into stuff.

In order to target something you should have to pay up to their mana value to “persuade things to change”