I have the feeling this might be little spewy readless but much more reasonable if we have reads (which we don't). The only potential read is that I usually see big donks like this as actually representative of a weaker hand. Fishier villains tend to x/r their big hands more often than they donk.

Also, even stronger players at 10nl don't have too much of a donking range multi-way (though I'm sure they should on some boards), so my initial view is that this is a weaker player who will also not recognize that this is not a good board to 3barrel as a bluff - so I don't think his range has changed much by the river except that it's more polarized as he's likely checking backing either turn or river with A8/89/78/79 type hands.

Anyways, I justify my call because I think he just has so much more air here than nuts - but am posting because I could be completely wrong.

PokerStars - $0.10 NL FAST (6 max) - Holdem - 6 players
Hand converted by PokerTracker 4

BTN: $12.12 (VPIP: 33.33, PFR: 22.22, 3Bet Preflop: 0.00, Hands: 9)
SB: $16.88 (VPIP: 25.33, PFR: 20.00, 3Bet Preflop: 3.85, Hands: 77)
BB: $11.24 (VPIP: 0.00, PFR: 0.00, 3Bet Preflop: -, Hands: 3)
UTG: $8.61 (VPIP: 50.00, PFR: 0.00, 3Bet Preflop: 0.00, Hands: 2)
Hero (MP): $18.39
CO: $9.55 (VPIP: 22.22, PFR: 5.56, 3Bet Preflop: 0.00, Hands: 19)

SB posts SB $0.05, BB posts BB $0.10

Pre Flop: (pot: $0.15) Hero has T T

fold, Hero raises to $0.30, fold, fold, SB calls $0.25, BB calls $0.20

Flop: ($0.90, 3 players) 4 8 5
SB checks, BB bets $0.86, Hero calls $0.86, fold

Turn: ($2.62, 2 players) 5
BB bets $2.50, Hero calls $2.50

River: ($7.62, 2 players) 9
BB bets $7.28, Hero calls $7.28

This is highly dependent on whether or not villain is just going to do this with his draws or also with his nutted hands:
Equity vs draws + nuts:
Board: 854
*******Equity*****Win*****Tie
MP3****42.61%**42.04%***0.57%*{ TdTs }
BB*****57.39%**56.81%***0.57%*{ 88, 55-44, 76s, 54s, KcQc, AcJc, KcJc, QcJc, AcTc, KcTc, QcTc, JcTc, Ac9c, Jc9c, Ac8c, Kc8c, 9d8d, 9h8h, 9c8c, 8d7d, 8h7h, 8c7c, A8o }

Equity vs primarily draws + some value hands we beat:
Board: 854
*******Equity*****Win*****Tie
MP3****53.45%**52.89%***0.56%*{ TdTs }
BB*****46.55%**45.99%***0.56%*{ A8s, 76s, KcQc, AcJc, KcJc, QcJc, AcTc, KcTc, QcTc, JcTc, Ac9c, Jc9c, A8o }

You make way too much (specific) assumptions about some you don't know. In addition, your stove can use some tweaks. Surely he might have some draws (although I find that unusual that he pots it), but don't put something like A8 in there, there is no reason to assume that.

This is a fold otr and maybe even ott.

Thanks - can you suggest a different range? That point in the second calc was to include that he may do this with worse value hands sometimes.

Also, what are the specific assumptions that you feel are out of place? My points at the top are all general assumptions but they could very well be wrong.

Well they are a contradicted. Kinda funny to read tbh.

You say stronger players don't donk (while good players will actually donk here).
So you assume he is weak/bad because he donk..

Then you assume because he is bad, he don't know this a bad board to bluf so he will tripple with all(?) his flop blufs. So you assume he has a weakish range otr! (But weak players don't really bluf much..).

So you assume that by donking pot 3 streets he has a weak range. Let me tell you, when someone does this on a wet multiway flop it is absolutely no sign of weakness!

Fair enough

He show up with 8's or 4's full or quads? That's the hands I would show up with there although I would of used a slightly smaller sizing unless I thought you were a fish.

He had QT

Can't see myself folding on this runout.