I haven't had time to test it, but try this. Open your game folder and navigate to file

\Endless Legend\Public\Quests\QuestDefinitions[DLC_21_B].xml

Open it, then find following block

    <!--============ TITLE: A raging fire  ============-->

    <QuestDefinition Name="DLC21_19ARagingFire" Category="SideQuest" SubCategory="Ruins"

                   Cooldown="0" SkipLockedQuestTarget="true" NumberOfConcurrentInstances="1" NumberOfOccurencesPerEmpire="1" NumberOfOccurencesPerGame="0">

        <!--============ TAGS ============-->

        <Tags>Interact</Tags>

        <!--============ PREREQUISITES ============-->

        <Prerequisites Target="$(Empire)">

            <DownloadableContentPrerequisite Flags="Prerequisite">DLC21Pack</DownloadableContentPrerequisite>

            <InterpreterPrerequisite Flags="Prerequisite">$Count(EmpireTypeMajor/ClassCity) ge 1</InterpreterPrerequisite>

            <!--<InterpreterPrerequisite Flags="Prerequisite">$Property(ClassEmpire:CurrentTurn) ge (40 * $Property(ClassEmpire:GameSpeedMultiplier))</InterpreterPrerequisite>

            <InterpreterPrerequisite Flags="Prerequisite">$Property(ClassEmpire:CurrentTurn) ge 40</InterpreterPrerequisite>

            -->

</Prerequisites>

Tag that you need is <InterpreterPrerequisite>, formatted above in bold. 

Change 

            <InterpreterPrerequisite Flags="Prerequisite">$Count(EmpireTypeMajor/ClassCity) ge 1</InterpreterPrerequisite>

line to

            <InterpreterPrerequisite Flags="Prerequisite">$Property(ClassEmpire:CurrentTurn) ge (80 * $Property(ClassEmpire:GameSpeedMultiplier))</InterpreterPrerequisite>

This should delay the quest to at least turn 80 on normal speed, sufficient to get to Era III with Titan bones.

You can enjoy Endless Legend "bug-free" (with or without DLCs) by installing the Endless Legend Community Patch (ELCP) - what is mandatory anyway. Past installation, you can choose (in game options), to add the bug-fixes for your game - only (at least I think so) - what should exclude the other improvements coming along with the ELCP, what you can activate/deactivate separately.

And/or you decide to get this workshop mod by the same modder and activate it past installation of ELCP:

https://steamcommunity.com/sharedfiles/filedetails/?id=1473002612

-> ELCP download thread:

https://www.games2gether.com/amplitude-studios/endless-legend/forums/15-modding/threads/30618-endless-legend-community-patch?page=1

For to be able to play Endless Legend mutliplayer with other users (in case you aim for), you need to have the same game version as all other players. What results in all players having ELCP installed, or not. How to uninstall ELCP is decribed in the linked thread above.