The crested form of this cactus presents the typical fan shape with a lumpy surface, adorned with thin whitish thorns that get reddish along the arch. Each exemplar has a unique shape, for this reason it is so much sought after by collectors. In its normal form T. thelegonus is part of the columnar cactaceae, which have a diameter not exceeding 8 cm, but can reach over 2 meters in height! For this reason, often its stems may arch and crawl on the ground, showing off thin spines with tonalities which vary from yellow to brown and contrast nicely with the opaque and tenuous green of the stem.