Help needed for a hero resource/stat.

Hello.

I develop a board game in which heroes fight monster and I was wondering if you could help me on something that I'm stuck.

I need a resource for my heroes that has to cover the following conditions:
1) Once the combat starts, this resource is initialized with 0.
2) It is increased as time passes.
3) It is spent by heroes to attack.
4) And the most difficult condition, it can be transferred form one hero to another.

At first I thought I could use "Time" as resource, but it cannot be transferred from one hero to another. (Is there any concept where time can be transferred from one hero to another ?)

Now, it doesn't have to be Heroes that fight. It is not strict. E.g. They could be either Summons or Golems.

Here is a list of all resources/stats that I have seen in games but none of these cover all 4 conditions :)

Resources: Hp, Stamina, Mana, Spirit, Rage, Fear, Magic, Courage, Momentum, Hunger / Thirst, Will, Power, Energy, Blood drain, Adrenaline

Any idea on what I could use as resource that cover the 4 conditions above ?

Thank you very much for your time !
Petros.