How to make invincible units

Hello. I’m creating a custom campaign but I need to make an onager unkillable or it won’t work as intended. I would like to know if this is possible and how to do it. Thanks for your attention.

Im not an expert, but isnt there a trigger on the editor to give them more HP or healing??

Yes, there is one trigger to increase hp and healing but they are limited. I want to make them unkillable. I saw in some scenarios units with a big negative number of hp that’s what i wanted to know.

You could make it that they can’t be targeted by attacks? Assuming of course that it won’t have to worry about splash damage. The negative number thing also works, but you would have to look it up to find out what it is.