You don't need to do any part of warzone 456 to access warzone 7. You will need to have completed the Recruitment mission of Bigfoot's Burden Quest in the warzone 123 area.
Before you can go into warzone 7, you need to do some basic tasks which are part of the Too Hot To Handle Quest which are:
1. Talk to Gnomystery and say favour to investigate a suspect of an unknown place in the crypt close to him
2. Talk to Brodraem Orcbeard and say mission/yes. He'll tell you unexpected incidents queered his pitch and that he'd like to clean the sarcoghapi more often.
3. Use the eastern-most tile of the closed wooden coffin near him to get useful items to complete the cleaning task. They are:
Walk north towards the fence where you will find the sarcoghapi covered in dirt, broken marble floors and ruined columns. Now use the items taken from the wooden coffin to fix these problems. In total you need to:
- Clean 5 sarcoghapi by using the brush on them.
- Repair 3 ruined columns by using the chisel on them.
- Cover 4 holes in the floor by using the marbel floors on them.
4. Report back to Brodraem Orcbeard and he'll tell you there might be chance to open the crypt again, and reward you with a White Gem.
5. Go back within the crypt, walk towards north and levitate down on the big crack. Once down, walk right and go through the teleport. You will be teleported to a room with 6 Diremaws and after walking around you'll get the message, "It feels like you should have heard about these creatures already." along with a questlog update.
7. Tell Gnomystery "news" and he inform you he will send out people to get more knowledge of the crypt.
8. Go back in the crypt and through the teleport and you will find Gnomevisor who is already expecting you. He will share details on how to explore the crypt using a crystal shield that is provided by them, however it is a very resourceful protection thus its protection is very weak and doesn't last long initially. For that reason it is recommended to only use it with the lowest heat level area. In order to upgrade the shield you will need crystal splinters, which are obtained by helping gnomes with research missions. To get to these missions you need protective layers which you obtain by killing monsters in the crypts.
Source: https://tibia.fandom.com/wiki/Too_Hot_to_Handle_Quest/Spoiler