Run this on your web browser on the Corncob page (http://www.mieliestronk.com/corncob_lowercase.txt) to get a list of anagrams for the word 'Undertale'.

.js

//Enter text string here.
s='undertale'

let d={}
let l=s.length
for(let c of s.split(''))d[c]=~~d[c]+1
let w=document.body.innerText.split('\n').map(v=>{
	a={}
	let i=0
	for(let c of v.split(''))
		if(!d[c])return
		else a[c]=~~a[c]+1,i++
	return[v,i,a]
}).filter(v=>v)

function f(d,l,s){
	if(!l)return[[]]
	else if(l<0)return[]
	let t=[]
	for(let[v,i,a]of w){
		if(!i)continue
		let h={}
		for(let i in d)
			if(!h)break
			else if((h[i]=d[i]-~~a[i])<0)h=null
		if(h)
			for(let b of f(h,l-i,v))
				t.push([v,...b])
	}
	return t
}

let r=f(d,l,s)
console.log(r)