Cometh, Cube

You summon a Gelatinous Cube next to you. This was entirely on purpose.

If you summon the Gelatinous Cube in a space occupied by a creature, the creature must make a Dexterity saving throw, jumping 5 feet in any direction on a success. On a failed save, the Gelatinous Cube enters the creature's space and immediately uses its Engulf ability, which the target creature is unable to save against. Regardless of whether the creature succeeds or fails on its saving throw, the Gelatinous Cube occupies the space it was summoned to.

The creature is an ally to you and your companions as long as you maintain Concentration on the spell that summoned it. In combat, the creature shares your initiative count, but it takes its turn immediately after yours. It obeys your verbal commands (no action required by you). If you don't issue any, it moves towards the nearest living creature and attempts to use the Engulf action.