Black Mesa (2019) - 16 - Gonarch's Lair [Hard]

Chapter 16: Gonarch's Lair
The teleporter Freeman used has landed him upon the island where the tower is located. However, before he can utilize another teleporter to get him to the tower proper, he is attacked by a deadly Xen creature known as the Gonarch. Able to take all of Freeman's arsenal without so much as a scratch, she chases him deep into her lair, filled with her headcrab offsprings and other Xenian creatures. Freeman must navigate the lair in a deadly cat and mouse game with the Gonarch and defeat her in a climactic battle if he is to continue on with his mission.

Playlist of completed chapters:    • Black Mesa (2019) - Full Playthrough ...  

Notes:
The spit attack of the Gonarch from HL1 has been replaced by a green mortar in BM. However, she still does have an alternate spit attack which launches the projectiles directly at you rather than at an arc
Unlike the HL1 Gonarch, she can charge the player in BM
In the first battle, the Gonarch will continue shelling the player with her mortar attack if the player stays on the healing pool as seen at 4:08
I really dig that title drop at 6:09
If the player had brought the yellow gas canister all the way from the second map of the Xen chapter (inside the lab), it can be teleported using the contraption at 7:55. The player will then find the canister in a hidden side passage during the final chase sequence with the Gonarch, by ducking into the hidden entryway on the left at 28:28. The canister can then be fed into a disperser which floods her lair with toxin, killing her almost instantly
Shooting the Gonarch in the area at 9:09 is possible but simply causes her to temporarily retreat behind cover. She will always come back and harass the player with mortars (from my experience)
Freeman can shoot her mortars out of the air, as seen at 29:36
The Gonarch breaks one of her hind legs from the fall shown at 30:02

Trivia:
In HL1, the Gonarch is already in the first area of the chapter when Freeman happens across it, rather than emerging from the ground once he has prepped the teleporter
There is no teleporter in the first area in HL1, as shown at 0:48. Gonarch's Lair in HL1 did end with a teleporter that you have to jump into after defeating her, though.
As seen by the beam at 2:48, it is highly probable that the portal Freeman is using would have placed him on or at the very least close to the tower, if it hadn't been destroyed
The second arena of Gonarch's Lair (shown at 13:55) is quite different from its HL1 counterpart. In BM, the Gonarch cannot be fought off, and staying above the webbing is not optional
The chase sequences, such as the ones at 16:22, could be a nod to similar chases with the Antlion Guardian in HL2EP2
The final area of the second map as seen at 18:11 can actually be seen earlier through a crevass located at 12:53
If the player does not shoot Gonarch at 19:05, she will use her mortar attack on the rocks once the player reaches the pond
Fast headcrabs can be seen very briefly at 20:35, but are otherwise not encountered ingame
Jumping onto the spiked plants at 18:29 will severely damage the player
The final arena as seen at 28:32 can actually be seen earlier in the map as shown at 19:24
In HL1, the player immediately falls through the webbing at 28:32 and has to fight Gonarch from the bottom of the pit
Just like in HL1's final arena, the Gonarch falls through the webbing after sustaining enough damage, as shown at 29:55
The Gonarch's death animation is somewhat different in HL1 - she will die upon collapsing on the floor, then violently shake and explode