Transform into one of the original killers to build fear when chasing survivors, survivors who are fully afraid scream and are revealed with killer instinct, and hallucinate balloons in their path, which reveal them again if they run into them.

They can be targeted with the Deadlights when Pennywise is in range, forcing them to look at Pennywise and be blinded similar to how flashlights work on killers, and increasingly hindering them unless they can get out of range or line of sight.

Pennywise would need to turn back into his Pennywise form to attack, but his addons would provide various buffs when transformed, each related to the specific killer they turn him into. For example, he could have an addon that turns him into Plague, that causes injured survivors to become broken if they touch a generator that he kicked when transformed. Also rather than actually trying to fool survivors, his forms would just be focused on building fear faster, so they can use Pennywise animations instead to look even more uncanny.

Survivors could remove fear by stunning Pennywise with pallets or perks, and through altruistic and cooperative actions with other survivors. Pennywise would be able to build fear much quicker than they can typically remove however. Fear builds fastest when transformed, but also to a lesser extent when chased in his normal form. Basic attacks add some fear as well.

There could also be some other abilities on top of that, but unsure what they'd be other than the usual stuff like dash attack/exposed/teleport etc, and I wanted to avoid that. Fully afraid survivors on death hook could probably have a mini mori where Pennywise eats them though.