Hadean Lands hints

I’ve been at this all day, trying to figure it out, though I’m sure I’m missing something obvious.
Here are my rituals/doors

[spoiler]You have learned thirty-four rituals: (* marks rituals you have not yet completed)
vacuum-protection synthesis ()
Gaian precipitate synthesis
coralicide synthesis
aura imitation inscription (with quartz)
lodestone of centrality creation
lead weight increase inscription
perfect mud synthesis
bamuriatic acid synthesis (
)
copper percalcinate synthesis
prophylactic scalpel inscription
clock tincture synthesis
metal attractor inscription
Great Marriage
dispersal brush creation
glass permeability inscription
aura imitation inscription (with jade) ()
viridigris synthesis
sublime spirit synthesis
lodestone of purity creation
electrum phlogistication (
)
aura impermeability inscription
aura invisibility inscription
gold ignition
planetary lens creation
breath-holding synthesis
fire-resistance synthesis
resonant oculus creation
fungicide synthesis
universal tarnish cleansing inscription (with the steel bolt)
universal tarnish cleansing inscription (with the brass pin) ()
doubled rust cleansing inscription (with the steel bolt)
doubled tarnish cleansing inscription (with the brass pin) (
)
basic rust cleansing inscription (with the steel bolt)
basic tarnish cleansing inscription (with the brass pin)

You have yet to deal with the following locked doors and barriers:
the Tertiary Lab door
the Airlock outer door
the Portico main doors
the North Arcade marble door
the Exoscaphe hatch
the obsidian door
the South Chasm bridge
the Garden Maze crawlway
the Storage Nook cabinet
fourteen fractures[/spoiler]

I know I need to:

Make lead weight decrease, though experimented with it in multiple ways
Get into the Tertiary lab
I’ve awakened Sydnesis, though I have no idea how to use him against the other dragons.

Help will be appreciated