Extremis Serum

The Extremis Serum is a bright orange-colored serum that was created and developed by Bruce Banner and Tony Stark.

Background
The Serum's sole reason for being made was to make it easier for Bruce to control his actions when he transformed into Hulk.

If a normal human injects themselves with Extremis, it can often have catastrophic results, such as spontaneous combustion, uncontrollable rage issues, and other physical and psychological defects.

Prototype
This version of the serum gave Bruce total control, but every time he injected it into himself, it'd force him to transform, and it wouldn't wear off until he transformed back into his human form.

Version 1
This updated version of the serum lasts much longer, even after Hulk turns back into Bruce, though it still requires multiple injections for it to work.

Venom-Extremis Mix
This version of the serum is mixed with Bane's Venom drug. When injected, it enhances Bane's already impressive strength to Hulk levels, though he burns through it too quickly due to his adrenaline.

After defeating Bane, Hulk burned all traces of this batch of the serum.

Users

 * Bruce Banner/Hulk: One of the creators of the serum and uses it to become a more in control version of the Hulk, who is more intelligent, capable of speaking in full sentences.
 * Becky: Took it to gain superpowers, much to Bruce Banner's frustration. Currently, she is cured of her abilities.
 * Unnamed homeless man
 * Several Children of Arkham: Given an unstable version of the serum by Lady Arkham and gained varied superpowers such as pyrokinesis and mind control.
 * Terrorists: Stole a perfected sample of Extremis and use their newly gained powers to kill lots of people. Currently, all of them were killed by Hulk.
 * Bane: Mixes it with his Venom drug so he could match Hulk's strength.