Consider the (producing Slime) versus the Supply Cupboard (producing Darkness). To upgrade your ability to summon a Golem, you might need high-tier Slime creatures, but to defeat a specific Champion, you need Darkness creatures. Your lair only has so many tiles. Every level 5 Bat (Darkness) you keep is a tile not used for a level 5 Eye Monster (Slime). This spatial sibling rivalry forces you to pick a "favorite" based on your current Feat requirements. The Feat System as the "Parent" The game’s Feat system acts as the exasperated parent, demanding that both "siblings" perform. A typical Feat might read: "Reach level 5 Werewolf AND level 5 Snake." This is where true rivalry turns into forced cooperation. You have neglected your Werewolves (Darkness/Altar) for days because Snakes (Slime/Chicken) were more efficient for damage. Now, you must pivot.
Adopt the "Merger’s Creed": No unit stays on the board unless it is merging toward a goal or actively producing resources. Damage units are disposable. If a Werewolf isn’t about to be used to kill something within the next two minutes, feed it to the Devourer. This resolves the rivalry instantly—the resource generator wins by default because the fighter is never allowed to loiter. Resolving the Rivalry: The Sibling Synergy Strangely, NecroMerger rewards you for occasionally ending the rivalry through synergy. The Archdemon (Darkness chain) and the Archangel (Mana chain) hate each other for space, but when combined via the Soul Grinder, they create bonuses that benefit both. Similarly, the Chicken (Slime chain’s egg layer) and the Altar (Darkness chain’s beast maker) are rivals for the same pool of Foul Chicken Eggs—but the Chicken needs space, and the Altar needs blood. Neither works well alone. sibling rivalry necromerger guide
A common beginner mistake is to over-invest in the "fighter" sibling. You keep three max-level Werewolves "just in case" a Paladin spawns. Meanwhile, the Mana-generating Skeleton sibling sits in a corner, starved of tiles. The result? You have muscle but no fuel. Consider the (producing Slime) versus the Supply Cupboard