I think Riven would be Undyne http://orig03.deviantart.net/aa16/f/2015/344/9/f/undyne___gyate_gyate___ohayou_by_pierrelucstl-d9jp6zc.png and if you got a problem with that
You can ether 1. http://orig05.deviantart.net/2295/f/2011/256/d/b/riven___the_exiled_whatever_by_thezatrox-d49mxx5.jpg
or 2. http://i2.kym-cdn.com/photos/images/newsfeed/000/181/828/lKRaa.gif
i don't know that game, so i'm going to post some random fish pic
http://orig13.deviantart.net/03a3/f/2013/219/a/1/slark_ohayou_by_artofhkm-d6h1lsk.png
inb4 obligatory Taric=Mettaton http://www.gifizer.com/gifs/in/65858121be771c92ed1641b530f6509a.gif
Uh... Sans? Sans the humor, of course. I just said that because he shows up everywhere and is scary as shit when you fight him.
Undyne. Neither will actually die when you kill them.
Hmm...
I'm gonna say Sans. He wants to have fun, hang out with people... But if you're an asshole, you're gonna have a bad time.
= https://media3.giphy.com/media/UCkZPALajEs8M/200.gif
they both teleport, nobody knows their history, and are annoying little shits that are my favorite personalities in the game.
Probably Undyne,because both have the same "Come at me bro!" attitude
That tree-mushroom thingy in the Tem Village
Well Darius would be.. Chara. But that's a long shot.
= Undyne. Both were single-minded in their beliefs and weren't afraid to kill in support of those beliefs. Then they meet somebody (Aspect and Frisk) and they end up becoming a lot more open-minded.
sans
they both teleport, both crack jokes, both make you pop like a friggin balloon, both pop outta nowhere with no warning, and both are smarter than they appear.
I main sona... she would be... METTATON?
Never played Undertale but from reading on wiki I would say Asgore.
Probably Undyne, if it were a matter of replacing the most similar character.
uhhhhhhhhh hmmm
I'm actually confused as to what 
would be
Possibly papyrus however papyrus isn't very violent ;x
Maybe Muffet?
Or possibly Grillby
Yeah prob Grillby https://gyazo.com/0b7faf5ba6ce621bc679ae4dfc818f42.gif
Hm, I actually think Gnar would be Sans. Normally chill and playful, just wants to goof off. But when he gets pissed....Oh boy.
+ 
+ 
= Undyne
= Undyne?
Undertale wasn't that good https://media.tenor.co/images/54451401d52c0dd2fe9ee5752857d53c/raw
wtf is undertale
CARE SPOOLERS
Undyne
Chara
goatmom
goatdad
mad dummy
Mettaton ex
Mettaton
sans
papyrus
alphys
gr8ter dog
lesser dog
doggo
amalgam8
flowey
goteboi
annoying dog
BURNS FIRESGUY
g4st3r
[lamb] snowy
the humans
monster kid
omega flowey
teh g0d of hyp3rd3th
What is undertale?
i dont have the slightest of clues... i watched one playthrough of undertale and i really didnt pay much attention lol.
I dunno about MF.
But I know Elise would be Miss Muffet.
Heimer would probably be Alphys.
