Why the specific encounter matters more than a generic boss recipe.
Interlude changes Antharas so that difficulty, rewards and the appearance of subordinate monsters depend on raid participation. Defeating subordinates can supply recovery items. Check the Interlude records for Antharas and Valakas when preparing your group. Advice for another version can assume different boss statistics or encounter rules.
For Antharas, Zaken, Baium, Anakim, Lilith, Valakas and Frintezza, the C5 rule returns a personally disconnected or restarted character to town on reconnect. A server crash has a separate exception for reconnecting within 30 minutes. Do not treat an ordinary client disconnect as that exception.
Do not use a planned relog inside one of the listed raid areas as a safe pause. The personal-disconnect rule can return the character to town, while the 30-minute exception concerns a server crash. Agree on a recovery and regrouping plan before entry, including what to do if a key party member loses connection. A disconnect is not evidence that the server-crash exception applies.