I’m about to start a Phandelver and Below campaign and I’m looking for suggestions on how to spice up the first half of the campaign as I feel it doesn’t connect well with the second half. One of the ideas was maybe replacing some of the early encounters with with chapter three with some aberrations type monsters to maybe advertise the affects the far realm is having on the surrounding area more early. Any thoughts on this? Would it be maybe to early in the campaign to showcase some of this? Any suggestions on monsters I could use? 

One thing I found important when running it was to introduce the mutant goblins early, through in some early encounters with them and make it clear there's something wrong about them compared to the Cragmaw goblins so the players know there's two threats out there and can start wondering about the crystal mutations. The encounter with the mutant cow is also a good thing to move to the first half of the campaign, I had it as one of the encounters between the Redbrand Hideout and Wave Echo Cave and used a reskinned Roper for the stat block. One thing the adventure does really badly and I found was vital to pulling it off as a single story was making the Black Spider connnected to the second half of the campaign. I ended up doing it that he was using his various plans and schemes to build a defence against the Mind Flayers so my players had an "oh crap, maybe we shouldn't have stopped him" moment when he died.

As written there's not too much connecting the Lost Mine portion of the adventure to the Shattered Obelisk portion. Doing things like linking the nothic, the Forge of Spells, or the Netherese expedition to the obelisk early on might help he adventures flow better together. Or maybe the Spider has found and is studying a piece of the obelisk, which in turn sets in motion the second half of the adventure? https://xender.vip/

Greetings Wesrin85,

Chiming in, as I too am planning to run PaBtSO in the near future for a newer group, and want to hear people's suggestions :)

Cheers!

I've now run Phandelver and Below three times in its entirety. I've run sections of it far more times. In additions I've run Lost Mine at least a dozen times. 

My experience has been that even if you do a lot of the work the lazy writing team ought to have done before the book was published, it does always show that these are two separate adventures. 

So, I run it as two separate adventures. After they've dealt with the Black spider, I tend to give the players some downtime. Maybe Phandalin has a village fair, or some kind of celebration. Have a minor quest where a player's child has gone missing in the nearby wilderness. After that I tend to launch a Psionic Goblin raid on the town. Alternatively in the D&D Adventurer Magazine series they had a cool little quest where some Cranium Rats had broken through the walls of the Stonehill Inn's cellar. They uncover a random artefact and skeleton, but they are a nice way of introducing 'hey, a new adventure is beginning'.

Allow the party to celebrate their success. Allow them some downtime, then run in the new adventure.