Use med brews, go naked, metal asc shield.

Firstly, your definitely going to want to clear the area around it first, (or lead it somewhere that’s isolated) because I was killed by mantis a few times trying to tame, then hit it to get its attention (it’s neutral) and block the bites or avoid, then let it hit you with its acid balls or vomit, you’ll get low doing that so make sure you have at least 2 stacks of med brews in your hot bar to use when low (there REALLY easy to make and early game) once at 3+ stacks of swallow/vomit it will suck you up, drop your useless asc items, It should only take 1-2, then it will knockout and you can mount it, then it asks for resources to swallow. 2026 taming process. :)