Here's what rhymes with costlye.
dry lie try ly ply rye lye pry tri trie wry lai luy pri spry by my high why apply die supply thy y buy cry fly guy tie vi hi shy sigh bi bye chi dye fi hy nigh pi pie thai thigh vie dei fry psi quae sly ty wir awry hai mai muy nai belie cy fy kai mei sy tai thei wai phi slier reply sky thereby deny imply rely comply hereby defy spy underlie decry pupae overlie sty ossify retry stye turfy lanai ripply justify nearby whereby alkali classify verify certify goodbye alibi amplify pacify samurai terrify untie descry edify resupply vilify aquae bonsai deify firefly triply ultrahigh amebae blowfly calcify horrify misapply stupefy overfly scurfy barfly shanghai vitrify drachmai banzais overbuy occupy satisfy stimuli modify multiply nuclei qualify specify simplify testify butterfly glorify gratify notify purify quantify alveoli fortify nullify ratify standby unify beautify falsify lullaby termini typify amoebae codify crucify mollify mortify oversupply ramify acidify mystify stratify stultify vivify petrify scarify versify hyperbolae mummify prettify speechify dandify yuppify clarify signify diversify magnify rectify solidify dignify liquefy emulsify reclassify reunify cumuli liquify declassify beatify gentrify refortify syllabify identify exemplify personify demystify detoxify dragonfly electrify preoccupy revivify dissatisfy solemnify intensify disqualify indemnify objectify oversimplify misidentify transmogrify