Water + Fire (Hydroflyx + Pyrobane)
Challenge: Heat Transfer: Defeat Hydroflux and Pyrobane without anyone in the raid getting more than 13 stacks of Engulfed or Drenched.
If raid have enough dps - you kill Water, then you kill Fire. Do not forget to dps Ice Tombs as well.
If raid do not have enough dps - when called "swap" or "go out" - you need to go outside of the big circle around the boss (to the entrance, "safe zone"). Then when you hear "go back" or "go in" - you are going to other boss (so if you was on Water, then you go on Fire, then you go on Water, and so on). Repeat until they are dead. Do not forget to kill Ice Tombs and Volcanoes on the way.
Do not forget that any damage from bosses will increase stacks of debuff and fail challenge. So dodge Fire waves and circling water line. If you have too much stacks (11 or more) and raid is trying challenge, just run away and jump down.
Water + Air (Hydroflyx + Airelon)
Challenge: Whiteout: Kill them before they finish their third midphase.
Do not hit Air boss from a side where it have Windwall ("Banana"), or it will throw everyone back, and can kill alot people by throwing them outside of the battlefield. If you got twirl (you will be cunfused and your movement keys would shuffle) - try to run to other boss and there run into the Ice Tombs.
Water + Logic (Hydroflyx + Mnemesis)
Challenge: Escaping the Crystalline: Do not let Raging Rapid’s hit three of the Logic Wall cubes.
Most likely it will be burn, so do NOT kick the boss, do not collect orbs and never deliver them to boss. If you are stalker - do not use clones, or if youare using clones, then select Water pair (so clones will hit Water pair and not kill people by hitting/kicking Logic pair). Kite the snake outside of the raid and move in circels. If you get any telegraph under you - move it outside of the raid (all of them are very harmful to raid).
Earth + Fire (Megalith + Pyrobane)
Challenge: The Floor is Lava: When Ragnarok is activated, no member of the raid can touch the lava on the floor or rock ablaze.
Follow Earth boss behind, then go to Fire boss, dodge flame waves. If midphase happened - jump on the rock and the jump between rocks, so you are never on the rock that is lighted up.
Earth + Air (Megalith + Airelon)
Challenge: Deep Impact: No raid members can die from falling when getting knocked up by Tornadoes, or Supercell.
Be in the front of the boss, take cleave with the tank. Less people in the cleave - more damage everyone will get. So always be in it (dodge all other red stuff). When raidcore is calling JUMP and raidlead saying Jump Jump - you do double jump (as Earth is casting Earthquake and it will stun and most likely kill everyone on the ground).
Earth + Logic (Megalith + Mnemesis)
Challenge: Cloud Computing: Do not allow more than one Pillar to be up at a time.
Just DPS bosses. If you get the Snake on you - go out of the raid and move in circles, running away from it somewhere far from players. If you get rock on you (rectangle telegraph that is following you) - place it between both bosses.
Life + Fire (Visceralis + Pyrobane)
Challenge: Fire Dancer: Kill the bosses without anyone in the raid taking damage from the Inferno Waves (it is bugged and never failing).
Dodge red, do not stack. You want to kill it before midphase or right after, otherwise it is one of the hardest fights.
Life + Air (Visceralis + Airelon)
Challenge: Annihilation Averted: Kill every Annihilation Orb during each mid phase.
Everyone is stacking at the same spot. All the time. It is very very very important. If you get twirl - go clear thorns. If you do not have twirl - stack with everyone else. Do not be outside of the stack, or you can cause a wipe. Never hit boss from Windwall ("Banana") side, or it can cause a wipe. Never dps the thorns. When thorns are spawned - do double dash backwards and you are fine.
Life + Logic (Visceralis + Mnemesis)
Challenge: Combinatorial Genomics: Finish midphase in 40 seconds or faster.
Never dps the thorns. Do not be behind tank. If you get snake - go out of the raid and kite her around. If your raid do not have enough dps to kill before midphase - take 2+ kicks and use kicks on cooldown (unless called otherwise).