This means you need to support your necromancers with towers that can destroy the first MOABs. This is especially evident in MOAB-type only rounds (necros dont get stacks from MOAB-types), where these MOABs move super slowly, and if you incorrectly place your necromancer, it can waste all of its stacks before it can even hit the MOAB, making it impossible to kill the first MOAB with only necros alone. The only problem is that if they will spawn even if there are no bloons going to their path, hence wasting their stacks. Late game = more bloons = constant max ammo = necro does more damage. The spawn rate is dependent on how many stacks they have. Necromancers only recharge their ammo when balloons die near the necro. The key to use necromancers properly is to understand 'prestacking' summons. Necromancers and especially Prince of Darkness are surprisingly strong for their cost to damage ratio and are top tier in many CHIMPS games.Remember to keep your budget in mind, and disable Monkey Knowledge for more realistic results. Even if it looked like a narrow loss, sometimes you need to entirely change the towers you use in order to beat those rounds. After getting a feel for the early and mid game strategies for a map, if you are not successful in completing CHIMPS, test your intended late-game strategies in Sandbox Mode first before retrying it is very frustrating to finally get to Rounds 90+ only to repeatedly lose to Rounds 95, 96, 98, 99 and 100, and start all over.If you spend too little money on defense, you will likely lose too early and not likely acquire necessary Activated Abilities in time to defend against difficult rounds.If you spend too much money on defense, you will likely fall in a dead end as you'll have little leeway for potential alternate defense planning.(Refer to the BTD6 Rounds for more details.) This generally lets you get 2 to 3 Tier 5 towers by Round 90+, along with the necessary support for them. Your budget by Round 40 is roughly $16k, by Round 63 is roughly $56k, by Round 78 is roughly $82k, by Round 90 is roughly $120k, and by Round 100 is roughly $170k.As there is no extra income from farms or other sources, it's worth saving money to place any essential towers when they are actually necessary for the defense.With the inability to sell your towers and the inability to continue after leaking a single life, any mistake in tower placement or ability timing can be unforgiving. It is wise to choose your towers and upgrades very carefully.While their placement is important to catch all bloons in the early game, do also make sure that they do not block the placement of more important towers in the mid to late game. Your options tend to be very limited in the early game, requiring you to get Dart Monkeys, Sniper Monkeys and Monkey Subs.Your early game strategy should set up for your mid-game strategy, and also late-game. You do not want to mix and match different towers to handle the early game, middle game, and late game. You will want a game plan of towers you want to build starting from round 6 all the way to round 100. Because there is no selling, pick towers that will be useful among all stages of the game and/or not cause a significant cost to the defense.