Bakragore's Burden is a mechanic to increase the difficulty of your bossfight against Bakragore in exchange of having higher chances of improving your loot, and earning more experience.
In order to activate the mechanic a team must have all four taints plus the final taint activated, as well as having essence which you can loot from Murcion, Vemiath, Ichgahal and Chagorz. Each miniboss has its own essence:
When using the lever to the final boss while having all taints, a team will first get teleported to an antechamber where they have 3 minutes to prepare for the fight and use their essences in devourers.
When an essence is successfully consumed an obelisk will appear close to the lever in the centre of the room and an orange message will be displayed on your screen: "The difficulty of the upcoming battle has increased!"
The difficulty is increased by stages. Each essence used increases the burden in one stage. As previously mentioned, there's both positive and negative sides, both of these improve in each stage as you can see below:
|Reduced damage dealt
|Increased damage taken
Additionally, using an essence will replace an Elder Bloodjaw in the fight with an Echo of the miniboss. Basically the miniboss itself instead of the summon.
Finally, the best benefit of triggering the burden is the chance of looting Grand variant of Sanguine equipment. This is a unique variant of the newest best-in-slot equipments that enhance spells from players using them. This is the only way players can loot them, making this variant very special (and likely very expensive as well).
Sources and references: TibiaWiki, Veyllor's stream on Twitch, Tschis' screenshot from Test Server