Letting someone else use one of your armies is always an odd prospect, in part because you build an army for your own play style, and that leaves a gap between what you have available and what they'd want. That said, I've got my Midnight Sorrow Harlequins vs my Ulthwe.
The Ulthwe list above has a take-all-comer vibe, designed to be flexible enough to face more elite forces like Castellan and friends, or hold up against more of a horde force. As a Brigade it boasts an impressive 15 command points.
The Harlequins are a force that is limited by my collection. In this case in order to squeeze as many points as I could from the list I split my Harlequin squads from 12 down to 6 troupers each. This allowed me to build two Battalions and add on a Vanguard detachment to total out 14 command points. this also required me to take the Webway Portal in order to hit the 2500. As it's basically playing with a handicap I took charge of the Harlequins.
The mission was #2 of the new Maelstrom missions, something like Head of the Snake. Essentially you comfortably generate new tactical objectives each turn, but when a character dies you lose an outstanding objective.
Deployment: We opted to have the objective markers overturned until after deployment, meaning we had no idea what objective was where. This made it tougher to remove objectives to refine the deck so I couldn't use my ordinary trick of removing the "defend objective" cards that are from my opponent's half of the board.
Harlequins would go first unless Ulthwe could seize. Both forces lined up, but Ulthwe was clearly prepared to absorb a charge and hold off its foes long enough to gather against the clowns, even having Fire Dragons in a Falcon preparing to take down the Webway Gate before the 6 Harlequins deployed in the labyrinthine depths of the webway along with a Death Jester. Unfortunately for the craftworld they did not seize, allowing the Harlequins to go first.
Player 1 Battle Round 1:
The Harlequins moved up aggressively, and thanks to the Shadowseer slingshotting a troupe up the field with a second move they managed to get into the front lines. The two units of Haywire bikes were okay against the Falcon and a Warp Hunter, but didn't destroy either, instead knocking them to their mid level profiles. The troupe that got into the thick of it finished off a Guardian squad and attempted to wrap up the farseer but couldn't get in behind him with the changes to the Flip Belts rule. In all the Harlequins got First Strike and achieved another objective whilst starting to defend an objective as well.
Player 2 Battle Round 1:
Looking to stem the tide the forces of Ulthwe quickly shifted position. The bikes leapt out to cut down the Troupe Master who I had foolishly left unaccompanied by a troupe (since they were in the Ulthwe lines). The fire dragons sped from the Falcon to take down the webway gate, but most of the units just shuffled around. The Wraithknight trundled forward to try and dominate the center of the board. A solid move as Harlequins often have trouble facing off against knights of any kind. In an unexpected turn Ulthwe was entirely shut down for the psychic phase. The Farseer had been placed in hopes of eliminating the troupe that was in the frontlines with Executioner and the bikes with smite, but both powers got denied, as did Jinx. In fact Jinx and Executioner were denied with box cars. The neutering of the psychic phase made a huge dent in the potential for the craftworld forces. They did eventually manage to kill the troupe and the closest unit of bikes, after putting unholy amounts of firepower into them, but it meant that little could be done to damage the units that were quickly approaching. When the Firedragons fired, point blank, at the Webway gate the unit of 6 managed to do a total of 5 wounds. Considering I failed the one save I'd been required to make on it I just saw this as a reminder that Fire Dragons are overpriced given their unreliability combined with their frailty. They aren't like Wraithguard, who can survive a bad round of fire, and take considerable effort to eliminate. The bikes laid a tremendous amount of firepower into the Troupe Master, but with his 3++ he shrugged off all but 3 wounds. The bikes charged him, hoping to finish off the last two wounds and net Warlord, but failed, and lost two of their number, one to the Heroicly Intervening shadowseer. Ulthwe was positioned to defend two objectives in the next turn, and had secured first strike, but hadn't had immediately achievable goals, discarding a Defend Objective that was on the Harlequin side of the board.
Player 1 Battle Round 2:
This was a huge turn for the Harlequins. They disembarked all units in transports in a pincer move, while the jetbikes pushed forward up the center. For psychic powers a Shadowseer fogged the mind of the Wraithknight while another challenged it to a battle of minds and put two wounds on it. Another managed to place -1 to hit on a unit coming up the center of the board. Having success in the Psychic phase gave me a lot of confidence. This was followed up by the second unit of bikes using haywire to finish off the wounded Warp Hunter. I was, perhaps, even a bit cocky with 6 fusion pistols at point blank range with the wraithknight. Unfortunately 4 of the troupers were unfamiliar with the sidearm and completely missed the hulking monstrosity. The other two hit, but only one wounded and managed 4 damage. Ultimately an uninspiring fare. The Assault phase was fierce with the Solitaire getting in to the Spiritseer, the Troupe Master getting in to the Shadow Spectres as he could not be overwatched, and the bikes making it in to Dire Avengers while 3 troupes and a troupe master all made it in to assault with the wraithknight. A troupe fully armed with Harlequin Kisses managed to bring the Wraithknight down to 4 wounds. This made interrupting less appealing, but my opponent did in order to try get slay the warlord. His assault failed and the Harlequins proceeded to slaughter Dire Avengers, Guardians, Shadow Spectres, and the Solitaire slaughtered the Spiritseer. After it consolidating leaving it about 4" from the Autarch and Bonesinger... after the minor attempt of Utlhwe to strike back it was the end of the fight phase and I played the Fight Again strategy on the Solitaire... followed by the Troupe Master finally spiking a refund for the first time ever, getting a three CP stratagem for free. The Solitaire was a blur, slamming into the Autarch and Bonesinger. While the Bonesinger died to the brutality of Cegorach's Rose, the Autarch's force shield was impressively effective, only letting one strike through. While the Harlequins pushed ahead to 7 Victory Points the forces of Ulthwe were shattered to be forced to discard their Defend Objective cards when their characters were slaughtered, crippling their ability to score.
Player 2 Battle Round 2:
The Wraithknight left combat and was healed for 3 wounds. Then the psychic phase began and the Farseer was ready to Smite and Execute his way to vengeance. But again both his spells were denied, both with box cars! At this point it was readily apparent that Ulthwe's Warhost was crippled. All that was left was to see how many models could survive. The Autarch obliterated the Solitaire with his fusion pistol while the Warp Hunter wiped out the second squad of bikes. The fog stopped the Wraithknight from making much of an impact. They still had not managed to score any Plobjectives.
Player 1 Battle Round 3:
The Autarch was killed netting warlord and the Wraithknight was wrapped up again, but even with a troupe master they only dropped it to 2 wounds. By the end of the turn the Harlequins were set to defend an objective and were now comfortably leading 9-1.
Player 2 Battle Round 3:
The Farseer went nuclear, getting off Executioner, Mind War, and then a full size Smite, killing off a troupe squad, a Star Weaver, and the Troupe Master, thanks to the objectives he was set to achieve maxed out two D3 objectives, pulling in 7 Victory Points. Outside of that MVP performance the Ulthwe forces managed to do little other than kill a Void Weaver and the Wraithknight did pretty much nothing useful while fogged. The loss of the Troupe Master meant I lost the ability to score the Defend Objective I'd been working on.
Player 1 Battle Round 4:
Virtually all of the troupes had been destroyed, leaving just a handful of harlequins, but they were still moving to capture objectives, bumping up from 9 to 15 points.
Player 2 Battle Round 4:
Only 2 wounds were left on the Wraithknight. It couldn't defend its objective with the expected movement of the Harlequin model, so it would need to live through the next turn and then hope the game continued and then live through the next turn to defend the objective.
Players 1-2 Battle Round 5:
Harlequin Victory 22-8.
This game confirmed the difficulties that Harlequins have with knights. Even a single knight can cause problems for them, and this is without the ability to shift it to a 3++ against shooting. a full knight force is basically a hard counter to them, because the bikes are so easy to take out for knights.
I feel like the Harlequin dominance of the psychic phases in turns 1 and 2 swung the game hard in favour of the clowns. It required so much extra firepower to rout them from the Ulthwe force's front lines.
In this particular mission the Defend Objectives are such a liability because they can't be scored instantly, thus making them more likely to be unachievable because you lost a character. All in all it was a fun game, but really cemented my thoughts about certain weaknesses in both armies and just how impressive certain units can be in the right circumstances (looking at you Solitaire).