What is your must-have metroidvania mechanic?
What elevates a MV from good to great?
I'm torn between "Every Weapon is a Tool" and "Sequence-Breaking".
Every Weapon is a Tool (all attacks/abilities/weapons can be used in combat/traversal and to pass ability gates. There are no "just a key" or "just a weapon" with no other use).
Sequence-Breaking (or multiple routes / able to mix up ability collection order / non-fixed progression path).
If I had to pick one I'd probably say Every Weapon is a Tool, especially when the tools are multi-purpose or the ability gates have multiple solutions.
What's yours?