BB looks just as surprised as the leader for a moment before trying to hide it,

"Ya! Like that!"

They pick themselves up, snarling at BB as they extend their staff and send a warbling orb of reality bending magics at him.

Attack: 23 Damage: 7 psychic damage

The attack passes over BB's head, and the leader looks disgusted with himself, retreating further into the rubble as more of his underlings can be heard approaching... including some large crunching footsteps.

Keller: 21 <----<<
Skitterers: 20 (?/?/?/?/?)
Grandpa: 19  
Black: 19 
Hulking Figure: 16 (?)
Larry: 15
Brynn: 15
Bolt: 11  
Skitterers: 8 (X,X/X/-X/-9/X)
Skitterers: 4 (X/?/?/?/?)
Hulking Figure: 2 (-103) (oops, lost track... it's a lot)
BB: 2  
Leader: 2 (-68ish)

BB winces in anticipation of getting blasted again but watches as the ball shoots past. He turns and points at the leader,

"HA! Sucks don't it?"

Can Keller get within 60 feet with a 30 foot movement? And if not, 30 feet BA dash?

((Keller is currently 60 ft from the leader, and has 4 skitterers that are surrounding Grandpa and Black within 20-35 ft. The turn that he was range limited on the crossbow was two turns ago, he hustled forward and hurled some acid at the leader last turn.))

((The white is just because I ran out of room in the upper corner of that massive map.))

Keller casts hold person on the leader, assuming he looks like a humanoid. WIS 14 save.

He then casts ray of frost on the nearest skitterer (unclear if I'd need to quicken the spell to be able to cast it as a bonus action, but I will if needed).

Attack: 22 Damage: 11 and speed drops 10 feet

He then backs up 30 feet, to the SE

((Keller, make an Arcana check for me please?))

Keller arcana (rolled in game log): 10

It's got two arms and two legs, but doesn't look like any humanoid race that Keller's seen before. He's not confident in either direction about whether hold person would work on the leader.

In that case, Keller, who is pretty beat up, backs up 20 feet south casts chaos bolt on the leader, using tides for advantage. It's a bonus action thanks to the last wild magic surge roll.

Attack: 22 Damage: 11 (force damage plus 3)

He then fires his second chance crossbow at the leader:

Attack: 9 (even with the reroll) Damage: N/A

((Keller Surge Check: 1))

((The previous surge only allows you to cast a leveled spell as an action while casting a spell as a bonus action on the same turn, would still need quickening to convert a spell from action to bonus action if it is not otherwise normally a BA. Temp HP don't apply unless both action and bonus action are used to cast spells.))

The leader, seeing Keller's warbling bolt of force incoming, makes use of the charging hulk's size and strength by swapping places with them, the chaotic bolt slamming into the second hulking figure, who bellows in pain and glares at Keller.

The newly arrived skitterers dash towards BB, but the rubble slows them to where two are able to get close, but none are able to attack him this turn.

Keller: 21
Skitterers: 20 (?/?/?/?/?)
Grandpa: 19   <----<<
Black: 19    <----<<
Hulking Figure: 16 (?)
Larry: 15
Brynn: 15
Bolt: 11  
Skitterers: 8 (X,X/X/-X/-9/X)
Skitterers: 4 (X/?/?/?/?)
Hulking Figure: 2 (-103) (oops, lost track... it's a lot)
BB: 2  
Leader: 2 (-68ish)

((As these are tiny creatures can Gramps move in between the two skitterers above him to the other side without attack of oppertunity against? If yes he will do the and cast Tasha's cautic brew trying to catch all four (but I think getting 3) and trying to not hit Bryn.

30ft 5ft line of acid shoots out of his wand. DC16 DEX save or take 4d6 acid damage at the start of its turn. After which he order Black to attack the skitterer not lid up that's currently above him.

Attack: 26 Damage: Unable to parse dice roll. Force damage. 

4 retry on dmg

((They're only small, not tiny, but since they by default snap to the upper left corner of the grid box they are in, I'm not to caught up on positioning, so am fine with Grandpa slipping between them. That being said, he can get 3 with the acid without hitting  Bryn, but could get all 4 if he wanted to risk an opportunity attack from one of them by shifting a bit to the west, sort of equidistant between Larry and BB?))

Ill take the attack of opportunity to get the 4.

Bite: Attack: 8 Damage: 7, if it hits, disadvantage DC 10 WIS save

Grandpa darts past the pair of skitterers and lines up a spray of acid, arcing it past all four of the ones that were moving to surround him.

The two he just moved past catch the full brunt of it, while those farther away are able to avoid at least some of the overspray of (13) acid. The injured Black limps forward to attack one of them, seeking to finish them off.

The hulking figure, having taken the damage from Keller meant for the leader, bellows and charges around the edge of the battle towards him. Bryn, caught close to the huge creature, disengages and scrambles up some rubble to the side, shouting a warning to his Commander as he takes a shot at the leader, sending a blast of cold at them.

Attack: 14 Damage: 14

Larry moves to intercept the hulk, raining blows down on them.

Attack: 21 Damage: 8
Attack: 21 Damage: 11
Attack: 17 Damage: 7

Keller, at 4hp, gulps as yet another hulking figure charges him. (How far away is he?)