If Berytos decides to keep pushing, I'm not sure I recover at all. Sailing is insanely powerful on this map, and losing provinces like that wrecks my income.
Mutual Assured Destruction. 
With Tir loosing much less than you in his invasion of my lands and me being much less efficient with sailors raiding him (wasn't as easy to attack him from the back and I didn't scout him as much), I couldn't keep my capital if I didn't retreat my troops from your lands.
Anyway, it's pretty clear in the graphs when you and Tir attacked me, and I couldn't get back in the competition afterwards. My lack of experience with Berytos failed me there, with me not summoning sacred goats early and not recruiting enough sacred units. I should also have inspected both Tir and your units to understand how my "mass javelins" could not stand a real chance agaisnt Tir (he simply let me attack then assassinated the commander more than once) nor against your biggest armies (cause you had, you know, spell-casters).
Yeah, the moment your first raiding group made landfall on the shores of my nation, I immediately dispatched assassins to provinces that I suspected of being targets for raiding. It may have seemed like I had assassins everywhere, but really I think I only had 4. I would simply make an assessment on where your next target would be and sent an assassin over there to intercept your raiding group. I would assassinate the commander and attack with a small skirmish group on the same turn and watch as all those commanderless spearmen would flee back into the sea. I think buying at least 1 PD in the provinces you raided would have made this much more costly for me, since I would then have to actually fight all those spearmen, which would have resulted in casualties on my side.
Once I captured your fort on my frontier and you counter-attacked with what seemed like everything you had (research mages included?), I just held up in my newly captured fort and rounded up the assassins. So those 4 assassins sallied forth from the fort each turn to assassinate one of your commanders/mages until the walls finally fell and I simply marched out to fight your army that was seriously depleted of magical support. I think putting a few soldiers on "Guard commander" for your mages might have helped you a lot, as my assassins weren't kitted out very heavily, they had a handful of acorns and that was it. Those same assassins ended up meeting sticky ends at the hands of Machaka (who had actually assigned guards to some of the 'less-fighty' commanders)
When I made the run for Machaka's water throne I actually had a rather small task force of necromancers and lords equipped with Shambler skins for water breathing and supported by dispensable mercenaries to fight their way into Machaka's lands. Unfortunately the resistance I met managed to knock out a couple of my Sidhe Lords who were crucial in protecting the necromancers for the upcoming underwater fight. This wouldn't have been a big problem as I had plenty of Sidhe Lords accompanying that group. The problem was, those Shambler skins I needed for underwater breathing were picked up by the mercenary captains and they stubbornly refused to give them back. So I sent my necromancers into that water province without any thugs to tank for them. Still, I expected a handful of necromancers firing off a shadowblast and then summoning skeletons to fight would be able to take on a bunch of wimpy mermen. I completely underestimated how fast Shark Tribe warriors could move. It didn't end well, and it set me back a few turns as I had to recruit a few more necromancers. In the meantime I just gave my surviving assassins some shambler skins and sent them in to assassinate the mermen commanders (I should have done that to start with).
All this delay allowed Yomi to come in and take the level 2 throne from that Sidhe-murdering Titan. This didn't matter to me much since I gave him my blessings in the first place and I was expecting to win the game a few turns before he was able to do anything with that throne anyways. One teleporting totem later and Yomi wins. Yikes! Serves me right for not making sufficient preparations. I originally planned to send a bunch of Tuatha down into that province for defense against R'lyeh early in the game, but somewhere between the birth of that thought and the war with Berytos I completely forgot about it.