At first I thought it was icelandic, because min timi &c, but determining the meaning is quite easy even without me speaking any non-english germanic language. Let's treat it like it's an unknown germanic language (as it is) and pretend I'm an archaeological linguist and we can reconstruct it.
'min riket' is 'my kingdom', cognate to mein reich or mijn rijk or whatnot. English lost the word rike a while back, replacing it with kingdom (from something like cyningtum)
'dine undergang' is 'your demise', cognate to thine undergoing. English doesn't use that metaphor for downfalls, possibly out of French influence, but it should be obvious to many english speakers nonetheless because of the german movie 'der untergang' ([the] downfall) unless they interpreted that title (as I have heard people do) as 'the group of people underground (in a bunker)' due to an undergang totally making sense in english in that way as a new coining.
'Mote': If I had to guess, I would first assume it's cognate to english 'makes' or german 'macht' via old norse 'makt' (-> mot...-e?), meaning 'causes/power', but that's completely a guess I would say if I were looking at an unknown language. Unfortunately, standard germanic grammar doesn't use a vowel ending for 3rd person singular, it'd be möt if that's even a valid word, so we can rule that out. Mote also could be meeting (cognate with 'meet' or 'moot' as in lawmoot in english- umlaut alternation in germanic is common, consider 'foot' vs 'feet' and 'goose' vs 'geese'), which would make more sense, but mote would thus be a noun unless it's been verbed.
If it's a verb that means 'causes', 'og' would have to be a particle like 'future tense' or a subordinator like 'which', but it isn't because that's not cognate with anything else, so we can assume 'og' means 'and'. It is cognate with one of the words for and in latin, 'ac'. Since 'and' is there, standard germanic syntax would imply there has to be a noun after it, meaning akin to moot is the best option.
That would seem to not make sense as it'd be Noun Possessive Noun, but I guarantee 'dine' is the genitive form of 'you', meaning 'of your', because that's the only thing that fits in germanic syntax in that position. We know this because even without speaking any scandinavian language, we can be pretty confident that german 'dein' is the base form of their pronoun and additions are given for things like female or, in this case, possessive. (At least in germanc languages, having the base be, say, 'deine' and subtracting the vowel is less likely).
This also tells us 'min riket' is non-genitive, as min is the basic form (again with analogy to the icelandic political phase 'min timi something something', the only piece of any scandinavian language I know). Riket however is non-basic. It could be a diminutive, but diminutive -t is more latinate than germanic, at which point I remember that -t is the 'definite' ending in some scandinavian languages, meaning it's a postfixed article akin to english 'the' as I suspected all along. Italians would understand il mio reggio or whatever, but in english we can thus ignore it for translation except to note it's literally 'the my kingdom' or something.
Thus I would translate it as 'the my kingdom and a meet of your doom', and clean that up to proper english as 'my kingdom, and a meeting with your doom'.
Whether it is swedish, danish, or norwegian is unknown to me, but it's definitely scandinavic. At this point I start to cheat a little and look up two words in swedish- downfall and 'and'. Since swedish uses 'och', not 'og' for and because of its innovation away from standard north germanic, and the speaker does not put an å for 'undergang', we can say it's not swedish with some uncertainty as swedes might just be lazy and not write out the å sometimes. But 'og' is a definite teller for west, not east, scandinavian.
But let's go with either norwegian bokmal, norwegian nynorsk, or danish. Since in a short sentence at that point even danes and norwegians might not be sure I am satisfied with that. They might be able to tell by the spelling or usage though, especially on the pronoun. I would guess against Danish and for Norwegian, Bokmal variant if I had to say, for reasons that are too complicated to go into as this post is already getting long.
I can do this without speaking a single word of language because I'm a linguist. Hopefully. Otherwise when a dane or norwegian comes in here and says it means something utterly different I'll look dumb.
(Other fun with languages- if you speak Latin, like Thanas, and have these instincts, you should intuitively understand the hindi insult 'tera maa ki' which I heard on an old episode of House recently.
Tera is something like Tuus (Te is a common PIE alteration with tu for the 2p sing pronoun, such as in, well, Latin 'te' or german dein), Maa is obviously 'mater' (it even has the long a), and ki is akin to latin 'quid' or, via what germanic languages did to initial PIE kw, 'which', but in this case appears to have degenerated into a genitive clitic from its stronger meaning of subordinating a clause.
Your mother's [left unstated, similar to how the english sentence trails off]