Requirements for Underworld Gate?

[myiqis50]

Hi. I just had access to the Underworld and wanted to build the Underworld Gate.

The construction cost is 500 gold and the message says "Can be built!".

However,when I click on "Build", a message says that "The fortress' upgrade level is too low to start this construction. Upgrade your fortress first".

I couldn't find any info on this from the manual or the internet so I'd like to ask if it's a bug or if I do need to upgrade, what exactly is needed? Is it the actual fortress level (I'm at level 13), or the fortress upgrade I see when I fight (106), or the fortress upgrade I see in the Hall of Fame (232) - speaking of which, why is the last 2 different in the first place?

Thanks!

[Edit: Turns out that the Heart of Darkness needs to be Level 2 which was not stated]

[DortSnort]

the fortress - the base is needed (I don’t even know what underworld is but that fortress is the only one in the game. No idea what other huge buildings with the name fortress u found)

[myiqis50]

The Underworld is a new update they had since last Oct.
If you have a level 10 gem mine and have access to the tower then you can find the Heart of Darkness (from the gem mine) which gives you access to the Underworld. :)

[Krpa]

Probably just a translation issue, but it should say that the heart needs to be leveled up a few times.

You worked it out though. Cheers. :)

[myiqis50]

yup, thank you! :)