“Last Stand” is episode sixteen of season five of Stargate SG-1.
In the previous episode, “Summit”, Daniel infiltrated a meeting of the Goa’uld System Lords with the intent of killing them all. When Osiris, who inhabits a body of Sarah, an old girlfriend of Daniel’s that he/she took possession of in “The Curse”, turns up unexpectedly as a representative of Anubis, he fails to kill them all.
Zipacna, who now serves Anubis after the absolutely final and definite death of Apophis in “Enemies”, launched an attack on the Tok’ra base and killed pretty much all of them. The rest of SG-1 were there, along with others including Lieutenant Elliot, from “Proving Ground”, who gets taken over by one of the Tok’ra after he is badly injured. Things do not look to be going well.
The rest of the System Lords had banished Anubis and tried to kill him – they thought successfully – so they aren’t happy to hear he has returned. This also means that if Daniel kills the rest of the System Lords, that will leave a power vacuum for Anubis to take over. Anubis was also banished because the rest of the System Lords found his crimes unspeakable. Which, for the Goa’uld, is saying something. They are hardly known for acting in a nice manner.