Collision of Pantheons

The world has many parallels. In each of them, a different deity or pantheon reigns supreme. They all cooperate and share in each others struggles and glory.
Until the outsiders find their universe. A singular world of gods with more pride, spite, and power than they could imagine. Some are friendly. Some are mischievous. And some are deadly. Most frightening part of them, they are completely unkillable, and no damage to them is un-regenerated within moments.
How shall the gods of Earth deal with these deities?
Let's find out.