I checked on line and one source said this is third person singular indicative but another source says that third person singular indicative is spolit. I would go with the latter because spoliat looks like subjunctive to me.
‘spoliat’ seems right. ‘spolit’ would mean that the infinitive is ‘spolire’…
It is indicative. It’s a 1st conjugation verb: spoliare. The -iat ending does look subjunctive as that is a common subjunctive ending found in 4th and 3rd -io verbs: audiat, capiat, dormiat, faciat, etc. Verbs in -iare aren’t very common but they do occur; I believe they are all denominative verbs: somniare from somnium, spoliare from spolium, etc.