Dying a lot? This is a walkthrough or tips and tricks for ROX’s Osiris (Ancient Pyramid instance mummy boss) to increase survivability.
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1. Stop at 34 or 67
Hit Osiris and stop at x34 for normal or x67 for hard. If you’re partying with strangers who may not follow this rule, perhaps stop earlier to prevent his HP from falling too much below 67 (which will trigger the black light too early).

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2. Wait for Osiris to summon Isis
The party should move away from the pillar where the first black light will come from (nearest left pillar from where you stand after the cut scene) because his next skill, Virus Swamp, will leave poisonous circles where some players stood at the time of the skill.

Members without the aggro can stand close to each other if you don’t want the circles spread out. After Virus Swamp, a member who can tank the damage from the black light can prepare to block the black light. The instant Osiris uses Undead Reincarnation (summoning some Isis) you can attack him.

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3. The jump

Steps 1 and 2 increase survivability because the jump resets the map, clearing the Virus Swamps and Isis.
When Osiris jumps, black light comes from the pillar and heals him if you don’t block it. Avoid crowding around the blocker or the next Virus Swamp will make it harder to block the light. If the party doesn’t have enough DPS, you don’t have to be in front of the pillar because the light will be blocked when you are anywhere between the pillar and Osiris. But you have to react fast when Osiris moves as the light will follow him.
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On subsequent jumps, more black lights will come from the pillars. The 2nd jump, there will be 2 lights and 3 on the 3rd jump. If you did everything right but still got to the 3rd jump, the party probably doesn’t have enough DPS.
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