The Cobalt mechanic is quite simple as well. But there are timers running in the background, which usually the commander keeps track of. Based on those timers you may want to continue the mechanic or wait; you want to stay together as one group.
There are three spots in the arena (called beach, jp, plank/mast/pole) where powder kegs can spawn. Only one spot will be active at a time. This spot will be marked with a red keg symbol on the map.
The active spot changes every two minutes (at 12:00, 10:00, 8:00, 6:00, 4:00 and 2:00 on the timer). The first keg spot is random. Kegs will never be on the same spot twice in a row.
Players have to go to the keg spot and interact (press "f") to pick up kegs, then carry them towards the wurm. Kegs must be placed by using skill 1 (a new skill you get when picking up a keg), on the dark spot in front of the wurm. This location will be marked with a red arrow during the event while holding a keg. When 20 kegs are placed here, the wurm will become vulnerable.
Do not use weapon-swap while carrying a keg (this destroys the keg).
Do not use teleportation skills while carrying a keg (this destroys the keg).
Do not fall into the water while carrying a keg (this destroys the keg).
Mounts can help you avoid falling into the water and move faster. However, falling into water while mounted will still remove your keg, with the exception of the Skimmer.
The Turtle mount cannot be used for carrying kegs (neither as driver nor passenger).
Be aware of the wurm's attacks when getting close to it/depositing kegs; orange aoe fields will indicate an incoming attack - dodge!
Rather take your time to get your keg safely to the deposit spot than hurrying and losing the keg, as you will have to wait until you can pick up another keg.
Kegs can only be held for 30s, so do not pick them up too early.
After you have picked up a keg, you have to wait 30s until you can pick up another one from the same keg spot. There is no cooldown for taking kegs from a different keg spot.
2min after a keg is placed, another keg will disappear - because of this, you want to run kegs as a group, so only when the commander tells you to run kegs; damage phases will not reset the timer.
Also, because of the keg-despawn-timer and the keg spot change timer, it might be better to not run kegs right away after you had a damage phase (always wait for the commander's call to run kegs on an organized map).
In addition, it might be needed to kill veteran wurms in the middle of the arena first to keep blockers (special team) safe and the deposit spot clear.
Stop damaging the wurm at ~10%. Slow down damaging a bit earlier, at ~15%, as the wurm will keep taking a bit of damage from conditions and people not paying too much attention. Do not run kegs while waiting for all 3 heads on the map to be ready to be decapitated to avoid unwanted keg despawns - until the commander will give the go-signal.