The Tesseract Vault and Obelisk are two configurations of the same dual-build Necrons super-heavy kit. The model hovers on a tall flight stand with no standard infantry base, so magnetization on this one is about getting the right flight stand height and locking the hull to whatever display or game base you run.
The Extra Large Flat – Tall Magnetic Flight Stand is the right height and strength for the Tesseract Vault.
For a basing magnet, use the Large Thick Flush-Fit Base Magnets, 6mm x 2.6mm. You will want to use 1 magnet if you transport the base separately and 2 if you transport the model on flight stand on the base.
[Buy Product=gw-flush-fit-base-magnets-large,variant=39439165882452]
If you would like a base with holes preset for magnets so the magnets can never pop out, use the 120mm oval base with magnet.
[Buy Product=bases-premagnetized-warhammer,variant=30427499921492]
For a flat bottomed base, use the Self-Adhesive magnets for an easy no-drill option.
[Buy Product=flexible-self-adhesive-magnets,variant=32934330728532]