My headcanon is that there are two ways to recover magic energy:
- Passively, through allowing atmospheric mana to flow into your vessel
- Actively, by forcing atmospheric mana inside the vessel
Headcanon is corroborated by Vetex saying the game limits it to charging, implying active charging exists in-lore but is not the only way to recover mana.
Since, as Vetex has said, you aren’t affected by not having mana, this means that passive recharge is cost-free. In my headcanon, active recharge would be faster but would put some stress on your soul/mind.
@anon1881879 already linked my post on the topic.